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>

retro/SKILL.md

@@ -95,6 +95,9 @@ git shortlog origin/main --since="<window>" -sn --no-merges
 
 # 8. Greptile triage history (if available)
 cat ~/.gstack/greptile-history.md 2>/dev/null || true
+
+# 9. TODOS.md backlog (if available)
+cat TODOS.md 2>/dev/null || true
 ```
 
 ### Step 2: Compute Metrics
@@ -130,6 +133,20 @@ Sort by commits descending. The current user (from `git config user.name`) alway
 
 **Greptile signal (if history exists):** Read `~/.gstack/greptile-history.md` (fetched in Step 1, command 8). Filter entries within the retro time window by date. Count entries by type: `fix`, `fp`, `already-fixed`. Compute signal ratio: `(fix + already-fixed) / (fix + already-fixed + fp)`. If no entries exist in the window or the file doesn't exist, skip the Greptile metric row. Skip unparseable lines silently.
 
+**Backlog Health (if TODOS.md exists):** Read `TODOS.md` (fetched in Step 1, command 9). Compute:
+- Total open TODOs (exclude items in `## Completed` section)
+- P0/P1 count (critical/urgent items)
+- P2 count (important items)
+- Items completed this period (items in Completed section with dates within the retro window)
+- Items added this period (cross-reference git log for commits that modified TODOS.md within the window)
+
+Include in the metrics table:
+```
+| Backlog Health | N open (X P0/P1, Y P2) · Z completed this period |
+```
+
+If TODOS.md doesn't exist, skip the Backlog Health row.
+
 ### Step 3: Commit Time Distribution
 
 Show hourly histogram in Pacific time using bar chart:
@@ -325,7 +342,18 @@ Use the Write tool to save the JSON file with this schema:
 }
 ```
 
-**Note:** Only include the `greptile` field if `~/.gstack/greptile-history.md` exists and has entries within the time window. If no history data is available, omit the field entirely.
+**Note:** Only include the `greptile` field if `~/.gstack/greptile-history.md` exists and has entries within the time window. Only include the `backlog` field if `TODOS.md` exists. If either has no data, omit the field entirely.
+
+Include backlog data in the JSON when TODOS.md exists:
+```json
+  "backlog": {
+    "total_open": 28,
+    "p0_p1": 2,
+    "p2": 8,
+    "completed_this_period": 3,
+    "added_this_period": 1
+  }
+```
 
 ### Step 14: Write the Narrative
 

retro/SKILL.md.tmpl

@@ -86,6 +86,9 @@ git shortlog origin/main --since="<window>" -sn --no-merges
 
 # 8. Greptile triage history (if available)
 cat ~/.gstack/greptile-history.md 2>/dev/null || true
+
+# 9. TODOS.md backlog (if available)
+cat TODOS.md 2>/dev/null || true
 ```
 
 ### Step 2: Compute Metrics
@@ -121,6 +124,20 @@ Sort by commits descending. The current user (from `git config user.name`) alway
 
 **Greptile signal (if history exists):** Read `~/.gstack/greptile-history.md` (fetched in Step 1, command 8). Filter entries within the retro time window by date. Count entries by type: `fix`, `fp`, `already-fixed`. Compute signal ratio: `(fix + already-fixed) / (fix + already-fixed + fp)`. If no entries exist in the window or the file doesn't exist, skip the Greptile metric row. Skip unparseable lines silently.
 
+**Backlog Health (if TODOS.md exists):** Read `TODOS.md` (fetched in Step 1, command 9). Compute:
+- Total open TODOs (exclude items in `## Completed` section)
+- P0/P1 count (critical/urgent items)
+- P2 count (important items)
+- Items completed this period (items in Completed section with dates within the retro window)
+- Items added this period (cross-reference git log for commits that modified TODOS.md within the window)
+
+Include in the metrics table:
+```
+| Backlog Health | N open (X P0/P1, Y P2) · Z completed this period |
+```
+
+If TODOS.md doesn't exist, skip the Backlog Health row.
+
 ### Step 3: Commit Time Distribution
 
 Show hourly histogram in Pacific time using bar chart:
@@ -316,7 +333,18 @@ Use the Write tool to save the JSON file with this schema:
 }
 ```
 
-**Note:** Only include the `greptile` field if `~/.gstack/greptile-history.md` exists and has entries within the time window. If no history data is available, omit the field entirely.
+**Note:** Only include the `greptile` field if `~/.gstack/greptile-history.md` exists and has entries within the time window. Only include the `backlog` field if `TODOS.md` exists. If either has no data, omit the field entirely.
+
+Include backlog data in the JSON when TODOS.md exists:
+```json
+  "backlog": {
+    "total_open": 28,
+    "p0_p1": 2,
+    "p2": 8,
+    "completed_this_period": 3,
+    "added_this_period": 1
+  }
+```
 
 ### Step 14: Write the Narrative