refactor(agentic): route file I/O through core.Fs

Replace raw os.* file operations with Core Fs equivalents:
- os.Stat → fs.Exists/fs.IsFile/fs.IsDir (resume, pr, plan, mirror, prep)
- os.ReadDir → fs.List (queue, status, plan, mirror, review_queue)
- os.Remove → fs.Delete (dispatch)
- os.OpenFile(append) → fs.Append (events, review_queue)
- strings.Replace → core.Replace (scan)

Eliminates os import from resume.go, pr.go. Eliminates strings
import from scan.go. Trades os for io in events.go.

Co-Authored-By: Virgil <virgil@lethean.io>

pkg/agentic/dispatch.go

@@ -125,7 +125,7 @@ func (s *PrepSubsystem) spawnAgent(agent, prompt, wsDir, srcDir string) (int, st
 
 	// Clean up stale BLOCKED.md from previous runs so it doesn't
 	// prevent this run from completing
-	os.Remove(core.JoinPath(srcDir, "BLOCKED.md"))
+	fs.Delete(core.JoinPath(srcDir, "BLOCKED.md"))
 
 	proc, err := process.StartWithOptions(context.Background(), process.RunOptions{
 		Command: command,

pkg/agentic/events.go

@@ -4,7 +4,7 @@ package agentic
 
 import (
 	"encoding/json"
-	"os"
+	"io"
 	"time"
 
 	core "dappco.re/go/core"
@@ -42,10 +42,11 @@ func emitCompletionEvent(agent, workspace, status string) {
 	}
 
 	// Append to events log
-	f, err := os.OpenFile(eventsFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err != nil {
+	r := fs.Append(eventsFile)
+	if !r.OK {
 		return
 	}
-	defer f.Close()
-	f.Write(append(data, '\n'))
+	wc := r.Value.(io.WriteCloser)
+	defer wc.Close()
+	wc.Write(append(data, '\n'))
 }

pkg/agentic/mirror.go

@@ -246,17 +246,18 @@ func filesChanged(repoDir, base, head string) int {
 
 // listLocalRepos returns repo names that exist as directories in basePath.
 func (s *PrepSubsystem) listLocalRepos(basePath string) []string {
-	entries, err := os.ReadDir(basePath)
-	if err != nil {
+	r := fs.List(basePath)
+	if !r.OK {
 		return nil
 	}
+	entries := r.Value.([]os.DirEntry)
 	var repos []string
 	for _, e := range entries {
 		if !e.IsDir() {
 			continue
 		}
 		// Must have a .git directory
-		if _, err := os.Stat(core.JoinPath(basePath, e.Name(), ".git")); err == nil {
+		if fs.IsDir(core.JoinPath(basePath, e.Name(), ".git")) {
 			repos = append(repos, e.Name())
 		}
 	}

pkg/agentic/plan.go

@@ -279,7 +279,7 @@ func (s *PrepSubsystem) planDelete(_ context.Context, _ *mcp.CallToolRequest, in
 	}
 
 	path := planPath(PlansRoot(), input.ID)
-	if _, err := os.Stat(path); err != nil {
+	if !fs.Exists(path) {
 		return nil, PlanDeleteOutput{}, core.E("planDelete", "plan not found: "+input.ID, nil)
 	}
 
@@ -301,10 +301,11 @@ func (s *PrepSubsystem) planList(_ context.Context, _ *mcp.CallToolRequest, inpu
 		return nil, PlanListOutput{}, core.E("planList", "failed to access plans directory", err)
 	}
 
-	entries, err := os.ReadDir(dir)
-	if err != nil {
-		return nil, PlanListOutput{}, core.E("planList", "failed to read plans directory", err)
+	r := fs.List(dir)
+	if !r.OK {
+		return nil, PlanListOutput{}, nil
 	}
+	entries := r.Value.([]os.DirEntry)
 
 	var plans []Plan
 	for _, entry := range entries {

pkg/agentic/pr.go

@@ -7,7 +7,6 @@ import (
 	"context"
 	"encoding/json"
 	"net/http"
-	"os"
 	"os/exec"
 
 	core "dappco.re/go/core"
@@ -58,7 +57,7 @@ func (s *PrepSubsystem) createPR(ctx context.Context, _ *mcp.CallToolRequest, in
 	wsDir := core.JoinPath(WorkspaceRoot(), input.Workspace)
 	srcDir := core.JoinPath(wsDir, "src")
 
-	if _, err := os.Stat(srcDir); err != nil {
+	if !fs.IsDir(srcDir) {
 		return nil, CreatePROutput{}, core.E("createPR", "workspace not found: "+input.Workspace, nil)
 	}
 

pkg/agentic/prep.go

@@ -250,12 +250,20 @@ func (s *PrepSubsystem) prepWorkspace(ctx context.Context, _ *mcp.CallToolReques
 		wsTmpl = "review"
 	}
 
-	promptContent, _ := lib.Prompt(input.Template)
+	promptContent := ""
+	if r := lib.Prompt(input.Template); r.OK {
+		promptContent = r.Value.(string)
+	}
 	personaContent := ""
 	if input.Persona != "" {
-		personaContent, _ = lib.Persona(input.Persona)
+		if r := lib.Persona(input.Persona); r.OK {
+			personaContent = r.Value.(string)
+		}
+	}
+	flowContent := ""
+	if r := lib.Flow(detectLanguage(repoPath)); r.OK {
+		flowContent = r.Value.(string)
 	}
-	flowContent, _ := lib.Flow(detectLanguage(repoPath))
 
 	wsData := &lib.WorkspaceData{
 		Repo:     input.Repo,
@@ -319,13 +327,13 @@ func (s *PrepSubsystem) prepWorkspace(ctx context.Context, _ *mcp.CallToolReques
 // --- Prompt templates ---
 
 func (s *PrepSubsystem) writePromptTemplate(template, wsDir string) {
-	prompt, err := lib.Template(template)
-	if err != nil {
-		// Fallback to default template
-		prompt, _ = lib.Template("default")
-		if prompt == "" {
-			prompt = "Read TODO.md and complete the task. Work in src/.\n"
-		}
+	r := lib.Template(template)
+	if !r.OK {
+		r = lib.Template("default")
+	}
+	prompt := "Read TODO.md and complete the task. Work in src/.\n"
+	if r.OK {
+		prompt = r.Value.(string)
 	}
 
 	fs.Write(core.JoinPath(wsDir, "src", "PROMPT.md"), prompt)
@@ -337,12 +345,12 @@ func (s *PrepSubsystem) writePromptTemplate(template, wsDir string) {
 // and writes PLAN.md into the workspace src/ directory.
 func (s *PrepSubsystem) writePlanFromTemplate(templateSlug string, variables map[string]string, task string, wsDir string) {
 	// Load template from embedded prompts package
-	data, err := lib.Template(templateSlug)
-	if err != nil {
+	r := lib.Template(templateSlug)
+	if !r.OK {
 		return // Template not found, skip silently
 	}
 
-	content := data
+	content := r.Value.(string)
 
 	// Substitute variables ({{variable_name}} → value)
 	for key, value := range variables {
@@ -649,7 +657,7 @@ func detectLanguage(repoPath string) string {
 		{"Dockerfile", "docker"},
 	}
 	for _, c := range checks {
-		if _, err := os.Stat(core.JoinPath(repoPath, c.file)); err == nil {
+		if fs.IsFile(core.JoinPath(repoPath, c.file)) {
 			return c.lang
 		}
 	}

pkg/agentic/queue.go

@@ -119,10 +119,11 @@ func (s *PrepSubsystem) delayForAgent(agent string) time.Duration {
 func (s *PrepSubsystem) countRunningByAgent(agent string) int {
 	wsRoot := WorkspaceRoot()
 
-	entries, err := os.ReadDir(wsRoot)
-	if err != nil {
+	r := fs.List(wsRoot)
+	if !r.OK {
 		return 0
 	}
+	entries := r.Value.([]os.DirEntry)
 
 	count := 0
 	for _, entry := range entries {
@@ -171,10 +172,11 @@ func (s *PrepSubsystem) drainQueue() {
 
 	wsRoot := WorkspaceRoot()
 
-	entries, err := os.ReadDir(wsRoot)
-	if err != nil {
+	r := fs.List(wsRoot)
+	if !r.OK {
 		return
 	}
+	entries := r.Value.([]os.DirEntry)
 
 	for _, entry := range entries {
 		if !entry.IsDir() {

pkg/agentic/resume.go

@@ -4,7 +4,6 @@ package agentic
 
 import (
 	"context"
-	"os"
 
 	core "dappco.re/go/core"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
@@ -48,7 +47,7 @@ func (s *PrepSubsystem) resume(ctx context.Context, _ *mcp.CallToolRequest, inpu
 	srcDir := core.JoinPath(wsDir, "src")
 
 	// Verify workspace exists
-	if _, err := os.Stat(srcDir); err != nil {
+	if !fs.IsDir(srcDir) {
 		return nil, ResumeOutput{}, core.E("resume", "workspace not found: "+input.Workspace, nil)
 	}
 

pkg/agentic/review_queue.go

@@ -5,6 +5,7 @@ package agentic
 import (
 	"context"
 	"encoding/json"
+	"io"
 	"os"
 	"os/exec"
 	"regexp"
@@ -134,10 +135,11 @@ func (s *PrepSubsystem) reviewQueue(ctx context.Context, _ *mcp.CallToolRequest,
 
 // findReviewCandidates returns repos that are ahead of GitHub main.
 func (s *PrepSubsystem) findReviewCandidates(basePath string) []string {
-	entries, err := os.ReadDir(basePath)
-	if err != nil {
+	r := fs.List(basePath)
+	if !r.OK {
 		return nil
 	}
+	entries := r.Value.([]os.DirEntry)
 
 	var candidates []string
 	for _, e := range entries {
@@ -361,11 +363,13 @@ func (s *PrepSubsystem) storeReviewOutput(repoDir, repo, reviewer, output string
 	jsonLine, _ := json.Marshal(entry)
 
 	jsonlPath := core.JoinPath(dataDir, "reviews.jsonl")
-	f, err := os.OpenFile(jsonlPath, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
-	if err == nil {
-		defer f.Close()
-		f.Write(append(jsonLine, '\n'))
+	r := fs.Append(jsonlPath)
+	if !r.OK {
+		return
 	}
+	wc := r.Value.(io.WriteCloser)
+	defer wc.Close()
+	wc.Write(append(jsonLine, '\n'))
 }
 
 // saveRateLimitState persists rate limit info for cross-run awareness.

pkg/agentic/scan.go

@@ -6,7 +6,6 @@ import (
 	"context"
 	"encoding/json"
 	"net/http"
-	"strings"
 
 	core "dappco.re/go/core"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
@@ -197,7 +196,7 @@ func (s *PrepSubsystem) listRepoIssues(ctx context.Context, org, repo, label str
 			Title:    issue.Title,
 			Labels:   labels,
 			Assignee: assignee,
-			URL:      strings.Replace(issue.HTMLURL, "https://forge.lthn.ai", s.forgeURL, 1),
+			URL:      core.Replace(issue.HTMLURL, "https://forge.lthn.ai", s.forgeURL),
 		})
 	}
 

pkg/agentic/status.go

@@ -113,10 +113,11 @@ func (s *PrepSubsystem) registerStatusTool(server *mcp.Server) {
 func (s *PrepSubsystem) status(ctx context.Context, _ *mcp.CallToolRequest, input StatusInput) (*mcp.CallToolResult, StatusOutput, error) {
 	wsRoot := WorkspaceRoot()
 
-	entries, err := os.ReadDir(wsRoot)
-	if err != nil {
-		return nil, StatusOutput{}, core.E("status", "no workspaces found", err)
+	r := fs.List(wsRoot)
+	if !r.OK {
+		return nil, StatusOutput{}, core.E("status", "no workspaces found", nil)
 	}
+	entries := r.Value.([]os.DirEntry)
 
 	var workspaces []WorkspaceInfo