fix(pidfile): replace path.Dir with filepath.Dir for cross-platform compat

- pidfile.go: use filepath.Dir instead of POSIX-only path.Dir (line 55)
- pidfile.go: simplify redundant bytes/string conversions to strings.TrimSpace (lines 44, 105)
- docs/RFC.md: add language identifiers to four untyped fenced code blocks (MD040)
- specs/api/RFC.md: update NewProvider signature to 3-arg form matching implementation

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

docs/RFC.md

@@ -14,7 +14,7 @@
 
 go-process provides the implementation behind `c.Process()`. Core defines the primitive (Section 17). go-process registers the Action handlers that make it work.
 
-```
+```text
 core/go defines:     c.Process().Run(ctx, "git", "log")
                      → calls c.Action("process.run").Run(ctx, opts)
 
@@ -37,7 +37,7 @@ The codebase now matches the v0.8.0 target. The bullets below are the historical
 
 ### File Layout
 
-```
+```text
 service.go        — main service (factory, lifecycle, process execution)
 registry.go       — daemon registry (PID files, health, restart)
 daemon.go         — DaemonEntry, managed daemon lifecycle
@@ -233,7 +233,7 @@ func (p *ManagedProcess) Info() ProcessInfo {
 
 Higher-level abstraction over `process.start`:
 
-```
+```text
 process.start  → low level: start a command, get a handle
 daemon.Start   → high level: PID file, health endpoint, restart policy, signals
 ```
@@ -256,7 +256,7 @@ return core.Result{Value: core.E("process.run", core.Concat("command failed: ",
 
 AX-7: `TestFile_Function_{Good,Bad,Ugly}`
 
-```
+```text
 TestService_Register_Good           — factory returns Result
 TestService_OnStartup_Good          — registers 5 Actions
 TestService_HandleRun_Good          — runs command, returns output

pidfile.go

@@ -1,9 +1,9 @@
 package process
 
 import (
-	"bytes"
-	"path"
+	"path/filepath"
 	"strconv"
+	"strings"
 	"sync"
 	"syscall"
 
@@ -41,7 +41,7 @@ func (p *PIDFile) Acquire() error {
 	defer p.mu.Unlock()
 
 	if data, err := coreio.Local.Read(p.path); err == nil {
-		pid, err := strconv.Atoi(string(bytes.TrimSpace([]byte(data))))
+		pid, err := strconv.Atoi(strings.TrimSpace(data))
 		if err == nil && pid > 0 {
 			if proc, err := processHandle(pid); err == nil {
 				if err := proc.Signal(syscall.Signal(0)); err == nil {
@@ -52,7 +52,7 @@ func (p *PIDFile) Acquire() error {
 		_ = coreio.Local.Delete(p.path)
 	}
 
-	if dir := path.Dir(p.path); dir != "." {
+	if dir := filepath.Dir(p.path); dir != "." {
 		if err := coreio.Local.EnsureDir(dir); err != nil {
 			return core.E("pidfile.acquire", "failed to create PID directory", err)
 		}
@@ -102,7 +102,7 @@ func ReadPID(path string) (int, bool) {
 		return 0, false
 	}
 
-	pid, err := strconv.Atoi(string(bytes.TrimSpace([]byte(data))))
+	pid, err := strconv.Atoi(strings.TrimSpace(data))
 	if err != nil || pid <= 0 {
 		return 0, false
 	}

specs/api/RFC.md

@@ -16,7 +16,7 @@ Exported fields:
 
 ### Package Functions
 
-- `func NewProvider(registry *process.Registry, hub *ws.Hub) *ProcessProvider`: Returns a `ProcessProvider` for the supplied registry and WebSocket hub. When `registry` is `nil`, it uses `process.DefaultRegistry()`.
+- `func NewProvider(registry *process.Registry, service *process.Service, hub *ws.Hub) *ProcessProvider`: Returns a `ProcessProvider` for the supplied registry, optional process service, and WebSocket hub. When `registry` is `nil`, it uses `process.DefaultRegistry()`. When `service` is non-`nil`, provider-runner features are enabled.
 - `func PIDAlive(pid int) bool`: Returns `false` for non-positive PIDs and otherwise reports whether `os.FindProcess(pid)` followed by signal `0` succeeds.
 
 ### `ProcessProvider` Methods