feat: safety hook skills + skill usage telemetry (v0.7.1) (#189)

* feat: add /careful, /freeze, /guard, /unfreeze safety hook skills

Four new on-demand skills using Claude Code's PreToolUse hooks:
- /careful: warns before destructive commands (rm -rf, DROP TABLE, force-push, etc.)
- /freeze: blocks file edits outside a specified directory
- /guard: composes both into one command
- /unfreeze: clears freeze boundary without ending session

Pure bash hook scripts with Python fallback for JSON edge cases.
Safe exceptions for build artifacts (node_modules, dist, .next, etc.).
Hook fire telemetry logs pattern name only (never command content).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add skill usage telemetry to preamble

TemplateContext system passes skill name through resolver pipeline so
each generated SKILL.md gets its own name baked into the telemetry line.
Appends to ~/.gstack/analytics/skill-usage.jsonl on every invocation.

Covers 14 preamble-using skills + 4 hook skills (inline telemetry).
JSONL format: {"skill":"ship","ts":"...","repo":"my-project"}

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add analytics CLI for skill usage stats

bun run analytics reads ~/.gstack/analytics/skill-usage.jsonl and shows
top skills, per-repo breakdown, hook fire stats, and daily timeline.
Supports --period 7d/30d/all. Handles missing/empty/malformed data.

22 unit tests cover parsing, filtering, formatting, and edge cases.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: add skills-used-this-week to /retro

Retro Step 2 now reads skill-usage.jsonl and shows which gstack skills
were used during the retro window. Follows the same pattern as the
Greptile signal and Backlog Health metrics — read file, filter by date,
aggregate, present. Skips silently if no analytics data exists.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* test: add hook script and telemetry tests

32 unit tests for check-careful.sh covering all 8 destructive patterns,
safe exceptions, Python fallback, and malformed input handling.
7 unit tests for check-freeze.sh covering boundary enforcement,
trailing slash edge case, and missing state file.
Telemetry tests verify per-skill name correctness in generated output.
Adds careful/freeze/guard/unfreeze/document-release to ALL_SKILLS.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* chore: bump version to 0.6.5 + changelog + mark TODOs shipped

Safety hook skills and skill usage telemetry shipped.
Analytics CLI and /retro integration included.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat: /debug auto-freezes edits to the module being debugged

Add PreToolUse hooks (Edit/Write) to debug/SKILL.md.tmpl that reference
the existing freeze/bin/check-freeze.sh. After Phase 1 investigation,
/debug locks edits to the narrowest affected directory.

Graceful degradation: if freeze script is unavailable, scope lock is
skipped. Users can run /unfreeze to remove the restriction.

Deferred 6 enhancements to TODOS.md, gated on telemetry showing the
freeze hook actually fires in real debugging sessions.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

freeze/SKILL.md

@@ -0,0 +1,82 @@
+---
+name: freeze
+version: 0.1.0
+description: |
+  Restrict file edits to a specific directory for the session. Blocks Edit and
+  Write outside the allowed path. Use when debugging to prevent accidentally
+  "fixing" unrelated code, or when you want to scope changes to one module.
+  Use when asked to "freeze", "restrict edits", "only edit this folder",
+  or "lock down edits".
+allowed-tools:
+  - Bash
+  - Read
+  - AskUserQuestion
+hooks:
+  PreToolUse:
+    - matcher: "Edit"
+      hooks:
+        - type: command
+          command: "bash ${CLAUDE_SKILL_DIR}/bin/check-freeze.sh"
+          statusMessage: "Checking freeze boundary..."
+    - matcher: "Write"
+      hooks:
+        - type: command
+          command: "bash ${CLAUDE_SKILL_DIR}/bin/check-freeze.sh"
+          statusMessage: "Checking freeze boundary..."
+---
+<!-- AUTO-GENERATED from SKILL.md.tmpl — do not edit directly -->
+<!-- Regenerate: bun run gen:skill-docs -->
+
+# /freeze — Restrict Edits to a Directory
+
+Lock file edits to a specific directory. Any Edit or Write operation targeting
+a file outside the allowed path will be **blocked** (not just warned).
+
+```bash
+mkdir -p ~/.gstack/analytics
+echo '{"skill":"freeze","ts":"'$(date -u +%Y-%m-%dT%H:%M:%SZ)'","repo":"'$(basename "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null || echo "unknown")'"}'  >> ~/.gstack/analytics/skill-usage.jsonl 2>/dev/null || true
+```
+
+## Setup
+
+Ask the user which directory to restrict edits to. Use AskUserQuestion:
+
+- Question: "Which directory should I restrict edits to? Files outside this path will be blocked from editing."
+- Text input (not multiple choice) — the user types a path.
+
+Once the user provides a directory path:
+
+1. Resolve it to an absolute path:
+```bash
+FREEZE_DIR=$(cd "<user-provided-path>" 2>/dev/null && pwd)
+echo "$FREEZE_DIR"
+```
+
+2. Ensure trailing slash and save to the freeze state file:
+```bash
+FREEZE_DIR="${FREEZE_DIR%/}/"
+STATE_DIR="${CLAUDE_PLUGIN_DATA:-$HOME/.gstack}"
+mkdir -p "$STATE_DIR"
+echo "$FREEZE_DIR" > "$STATE_DIR/freeze-dir.txt"
+echo "Freeze boundary set: $FREEZE_DIR"
+```
+
+Tell the user: "Edits are now restricted to `<path>/`. Any Edit or Write
+outside this directory will be blocked. To change the boundary, run `/freeze`
+again. To remove it, run `/unfreeze` or end the session."
+
+## How it works
+
+The hook reads `file_path` from the Edit/Write tool input JSON, then checks
+whether the path starts with the freeze directory. If not, it returns
+`permissionDecision: "deny"` to block the operation.
+
+The freeze boundary persists for the session via the state file. The hook
+script reads it on every Edit/Write invocation.
+
+## Notes
+
+- The trailing `/` on the freeze directory prevents `/src` from matching `/src-old`
+- Freeze applies to Edit and Write tools only — Read, Bash, Glob, Grep are unaffected
+- This prevents accidental edits, not a security boundary — Bash commands like `sed` can still modify files outside the boundary
+- To deactivate, run `/unfreeze` or end the conversation