feat: TODOS-aware skills, 2-tier Greptile replies, gitignore fix (#61)

* fix: log non-ENOENT errors in ensureStateDir() instead of silently swallowing

Replace bare catch {} with ENOENT-only silence. Non-ENOENT errors (EACCES,
ENOSPC) are now logged to .gstack/browse-server.log. Includes test for
permission-denied scenario with chmod 444.

* feat: merge TODO.md + TODOS.md into unified backlog with shared format reference

Merge TODO.md (roadmap) and TODOS.md (near-term) into one file organized by
skill/component with P0-P4 priority ordering and Completed section. Add shared
review/TODOS-format.md for canonical format. Add static validation tests.

* feat: add 2-tier Greptile reply system with escalation detection

Add reply templates (Tier 1 friendly, Tier 2 firm), explicit escalation
detection algorithm, and severity re-ranking guidance to greptile-triage.md.

* feat: cross-skill TODOS awareness + Greptile template refs in all skills

/ship Step 5.5: auto-detect completed TODOs, offer reorganization.
/review Step 5.5: cross-reference PR against open TODOs.
/plan-ceo-review, /plan-eng-review: TODOS context in planning.
/retro: Backlog Health metric. /qa: bug TODO context in diff-aware mode.
All Greptile-aware skills now reference reply templates and escalation detection.

* chore: bump version and changelog (v0.3.8)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: update CONTRIBUTING.md for v0.3.8 changes

Clarify test tier cost table (Tier 3 standalone vs combined), add TODOS.md
to "Things to know", mention Greptile triage in ship workflow description.

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

plan-ceo-review/SKILL.md

@@ -74,7 +74,13 @@ git stash list                                 # Any stashed work
 grep -r "TODO\|FIXME\|HACK\|XXX" --include="*.rb" --include="*.js" -l
 find . -name "*.rb" -newer Gemfile.lock | head -20  # Recently touched files
 ```
-Then read CLAUDE.md, TODOS.md, and any existing architecture docs. Map:
+Then read CLAUDE.md, TODOS.md, and any existing architecture docs. When reading TODOS.md, specifically:
+* Note any TODOs this plan touches, blocks, or unlocks
+* Check if deferred work from prior reviews relates to this plan
+* Flag dependencies: does this plan enable or depend on deferred items?
+* Map known pain points (from TODOS) to this plan's scope
+
+Map:
 * What is the current system state?
 * What is already in flight (other open PRs, branches, stashed changes)?
 * What are the existing known pain points most relevant to this plan?
@@ -393,7 +399,7 @@ Complete table of every method that can fail, every exception class, rescued sta
 Any row with RESCUED=N, TEST=N, USER SEES=Silent → **CRITICAL GAP**.
 
 ### TODOS.md updates
-Present each potential TODO as its own individual AskUserQuestion. Never batch TODOs — one per question. Never silently skip this step.
+Present each potential TODO as its own individual AskUserQuestion. Never batch TODOs — one per question. Never silently skip this step. Follow the format in `.claude/skills/review/TODOS-format.md`.
 
 For each TODO, describe:
 * **What:** One-line description of the work.

plan-ceo-review/SKILL.md.tmpl

@@ -65,7 +65,13 @@ git stash list                                 # Any stashed work
 grep -r "TODO\|FIXME\|HACK\|XXX" --include="*.rb" --include="*.js" -l
 find . -name "*.rb" -newer Gemfile.lock | head -20  # Recently touched files
 ```
-Then read CLAUDE.md, TODOS.md, and any existing architecture docs. Map:
+Then read CLAUDE.md, TODOS.md, and any existing architecture docs. When reading TODOS.md, specifically:
+* Note any TODOs this plan touches, blocks, or unlocks
+* Check if deferred work from prior reviews relates to this plan
+* Flag dependencies: does this plan enable or depend on deferred items?
+* Map known pain points (from TODOS) to this plan's scope
+
+Map:
 * What is the current system state?
 * What is already in flight (other open PRs, branches, stashed changes)?
 * What are the existing known pain points most relevant to this plan?
@@ -384,7 +390,7 @@ Complete table of every method that can fail, every exception class, rescued sta
 Any row with RESCUED=N, TEST=N, USER SEES=Silent → **CRITICAL GAP**.
 
 ### TODOS.md updates
-Present each potential TODO as its own individual AskUserQuestion. Never batch TODOs — one per question. Never silently skip this step.
+Present each potential TODO as its own individual AskUserQuestion. Never batch TODOs — one per question. Never silently skip this step. Follow the format in `.claude/skills/review/TODOS-format.md`.
 
 For each TODO, describe:
 * **What:** One-line description of the work.