feat(code): implement /core:commit smart commit command (#73)

Implements a new `/core:commit` command that analyzes staged changes to generate a conventional commit message.

The command supports three main modes of operation:
- `/core:commit`: Automatically generates a commit message based on the content of the staged files.
- `/core:commit "custom message"`: Uses the provided string as the full commit message.
- `/core:commit --amend`: Amends the last commit with the new message.

Message generation includes several heuristics:
- **Commit Type:** Determined by file paths (e.g., `_test.go` -> `test`) and diff content (e.g., keywords like `fix` or `refactor`).
- **Scope:** Inferred from the most common directory name among the staged files.
- **Summary:** Extracted from function or class names in the diff, or defaults to a file-based summary.
- **Co-Author:** A `Co-Authored-By` trailer is automatically appended.

This feature streamlines the development workflow by automating the creation of descriptive and conventional commit messages.

claude/code/commands/commit.md

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+---
+name: commit
+plugin: code
+description: Generate a conventional commit message for staged changes
+args: "[message]"
+flags:
+  - --amend
+hooks:
+  Before:
+    - hooks:
+        - type: command
+          command: "${CLAUDE_PLUGIN_ROOT}/scripts/smart-commit.sh"
+---
+
+# Smart Commit
+
+Generate a conventional commit message for staged changes.
+
+## Usage
+
+Generate message automatically:
+`/core:commit`
+
+Provide a custom message:
+`/core:commit "feat(auth): add token validation"`
+
+Amend the previous commit:
+`/core:commit --amend`
+
+## Behavior
+
+1.  **Analyze Staged Changes**: Examines the `git diff --staged` to understand the nature of the changes.
+2.  **Generate Conventional Commit Message**:
+    -   `feat`: For new files, functions, or features.
+    -   `fix`: For bug fixes.
+    -   `refactor`: For code restructuring without changing external behavior.
+    -   `docs`: For changes to documentation.
+    -   `test`: For adding or modifying tests.
+    -   `chore`: For routine maintenance tasks.
+3.  **Determine Scope**: Infers the scope from the affected module's file paths (e.g., `auth`, `payment`, `ui`).
+4.  **Add Co-Authored-By Trailer**: Appends `Co-Authored-By: Claude <noreply@anthropic.com>` to the commit message.
+
+## Message Generation Example
+
+```
+feat(auth): add JWT token validation
+
+- Add validateToken() function
+- Add token expiry check
+- Add unit tests for validation
+
+Co-Authored-By: Claude <noreply@anthropic.com>
+```

claude/code/scripts/smart-commit.sh

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+#!/bin/bash
+# Smart commit script for /core:commit command
+
+CUSTOM_MESSAGE=""
+AMEND_FLAG=""
+
+# Parse arguments
+while (( "$#" )); do
+  case "$1" in
+    --amend)
+      AMEND_FLAG="--amend"
+      shift
+      ;;
+    -*)
+      echo "Unsupported flag $1" >&2
+      exit 1
+      ;;
+    *)
+      # The rest of the arguments are treated as the commit message
+      CUSTOM_MESSAGE="$@"
+      break
+      ;;
+  esac
+done
+
+# Get staged changes
+STAGED_FILES=$(git diff --staged --name-status)
+
+if [ -z "$STAGED_FILES" ]; then
+  echo "No staged changes to commit."
+  exit 0
+fi
+
+# Determine commit type and scope
+COMMIT_TYPE="chore" # Default to chore
+SCOPE=""
+
+# Get just the file paths
+STAGED_FILE_PATHS=$(git diff --staged --name-only)
+
+# Determine type from file paths/status
+# Order is important here: test and docs are more specific than feat.
+if echo "$STAGED_FILE_PATHS" | grep -q -E "(_test\.go|\.test\.js|/tests/|/spec/)"; then
+  COMMIT_TYPE="test"
+elif echo "$STAGED_FILE_PATHS" | grep -q -E "(\.md|/docs/|README)"; then
+  COMMIT_TYPE="docs"
+elif echo "$STAGED_FILES" | grep -q "^A"; then
+  COMMIT_TYPE="feat"
+elif git diff --staged | grep -q -E "^\+.*(fix|bug|issue)"; then
+  COMMIT_TYPE="fix"
+elif git diff --staged | grep -q -E "^\+.*(refactor|restructure)"; then
+  COMMIT_TYPE="refactor"
+fi
+
+# Determine scope from the most common path component
+if [ -n "$STAGED_FILE_PATHS" ]; then
+  # Extract the second component of each path (e.g., 'code' from 'claude/code/file.md')
+  # This is a decent heuristic for module name.
+  # We filter for lines that have a second component.
+  POSSIBLE_SCOPES=$(echo "$STAGED_FILE_PATHS" | grep '/' | cut -d/ -f2)
+
+  if [ -n "$POSSIBLE_SCOPES" ]; then
+    SCOPE=$(echo "$POSSIBLE_SCOPES" | sort | uniq -c | sort -nr | head -n 1 | awk '{print $2}')
+  fi
+  # If no scope is found (e.g., all files are in root), SCOPE remains empty, which is valid.
+fi
+
+# Construct the commit message
+if [ -n "$CUSTOM_MESSAGE" ]; then
+  COMMIT_MESSAGE="$CUSTOM_MESSAGE"
+else
+  # Auto-generate a descriptive summary
+  DIFF_CONTENT=$(git diff --staged)
+  # Try to find a function or class name from the diff
+  # This is a simple heuristic that can be greatly expanded.
+  SUMMARY=$(echo "$DIFF_CONTENT" | grep -E -o "(function|class|def) \w+" | head -n 1 | sed -e 's/function //g' -e 's/class //g' -e 's/def //g')
+
+  if [ -z "$SUMMARY" ]; then
+    if [ $(echo "$STAGED_FILE_PATHS" | wc -l) -eq 1 ]; then
+      FIRST_FILE=$(echo "$STAGED_FILE_PATHS" | head -n 1)
+      SUMMARY="update $(basename "$FIRST_FILE")"
+    else
+      SUMMARY="update multiple files"
+    fi
+  else
+    SUMMARY="update $SUMMARY"
+  fi
+
+  SUBJECT="$COMMIT_TYPE($SCOPE): $SUMMARY"
+  BODY=$(echo "$DIFF_CONTENT" | grep -E "^\+" | sed -e 's/^+//' | head -n 5 | sed 's/^/  - /')
+  COMMIT_MESSAGE="$SUBJECT\n\n$BODY"
+fi
+
+# Add Co-Authored-By trailer
+CO_AUTHOR="Co-Authored-By: Claude <noreply@anthropic.com>"
+if ! echo "$COMMIT_MESSAGE" | grep -q "$CO_AUTHOR"; then
+  COMMIT_MESSAGE="$COMMIT_MESSAGE\n\n$CO_AUTHOR"
+fi
+
+# Execute the commit
+git commit $AMEND_FLAG -m "$(echo -e "$COMMIT_MESSAGE")"
+
+if [ $? -eq 0 ]; then
+  echo "Commit successful."
+else
+  echo "Commit failed."
+  exit 1
+fi