feat: GitLab support for /retro, /ship, and /document-release (v0.11.20.0) (#508)

* feat: multi-platform BASE_BRANCH_DETECT (GitHub + GitLab + GHE + git-native)

Update the shared BASE_BRANCH_DETECT resolver to support GitHub, GitLab,
GitHub Enterprise, self-hosted GitLab, and a git-native fallback chain.
Platform detection uses remote URL matching plus CLI auth status for
custom domains. Add glab issue create alternative in test failure triage.

Add 7 new test assertions covering GitLab CLI presence, git symbolic-ref
fallback, and platform-specific output in retro and ship generated files.

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

* feat: GitLab support in /retro — use shared BASE_BRANCH_DETECT resolver

Replace retro's custom gh-only default branch detection with the shared
BASE_BRANCH_DETECT resolver (DRY — same as 10 other skills). Update
PR/MR number extraction to match both GitHub #NNN and GitLab !NNN
patterns. Remove hardcoded github.com URL from the personal card footer.
Regenerate all SKILL.md files affected by the resolver update.

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

* feat: GitLab MR creation in /ship + /document-release

Ship Step 1.5 now checks .gitlab-ci.yml for release workflows alongside
GitHub Actions. Step 8 routes to glab mr create on GitLab repos with
correct flag mapping (-b, -t, -d). Falls back to manual instructions
when no CLI is available. Document-release now reads MR body via
glab mr view -F json and updates via glab mr update on GitLab repos.

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

* chore: add P2 TODO for land-and-deploy GitLab support

Track the remaining work to support GitLab in /land-and-deploy — MR
merge, CI polling, and deploy workflow detection using glab equivalents.

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

* fix: adversarial review — GitLab gate, shell safety, MR prefix preservation

Three fixes from adversarial review:
1. land-and-deploy: add GitLab gate after Step 0 — prevents detection/
   execution mismatch where agent detects GitLab but all subsequent
   steps are GitHub-only
2. document-release: use heredoc for glab mr update body to avoid shell
   metacharacter mangling ($, backticks, !) in MR descriptions
3. retro: preserve original #/! prefix in PR/MR number extraction —
   GitLab !42 stays as !42, not incorrectly converted to #42

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

* fix: resolve merge conflicts — deduplicate gen-skill-docs resolvers

The merge from main created duplicate RESOLVERS records in gen-skill-docs.ts
(inline functions shadowing the imported module versions). Removed the inline
duplicates so the modular resolvers from scripts/resolvers/ are used.
Also added missing E2E_TIERS entries for plan-completion/verification tests.

* chore: bump version and changelog (v0.11.20.0)

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

---------

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

retro/SKILL.md.tmpl

@@ -18,15 +18,7 @@ allowed-tools:
 
 {{PREAMBLE}}
 
-## Detect default branch
-
-Before gathering data, detect the repo's default branch name:
-`gh repo view --json defaultBranchRef -q .defaultBranchRef.name`
-
-If this fails, fall back to `main`. Use the detected name wherever the instructions
-say `origin/<default>` below.
-
----
+{{BASE_BRANCH_DETECT}}
 
 # /retro — Weekly Engineering Retrospective
 
@@ -95,8 +87,8 @@ git log origin/<default> --since="<window>" --format="%at|%aN|%ai|%s" | sort -n
 # 4. Files most frequently changed (hotspot analysis)
 git log origin/<default> --since="<window>" --format="" --name-only | grep -v '^$' | sort | uniq -c | sort -rn
 
-# 5. PR numbers from commit messages (extract #NNN patterns)
-git log origin/<default> --since="<window>" --format="%s" | grep -oE '#[0-9]+' | sed 's/^#//' | sort -n | uniq | sed 's/^/#/'
+# 5. PR/MR numbers from commit messages (GitHub #NNN, GitLab !NNN)
+git log origin/<default> --since="<window>" --format="%s" | grep -oE '[#!][0-9]+' | sort -t'#' -k1 | uniq
 
 # 6. Per-author file hotspots (who touches what)
 git log origin/<default> --since="<window>" --format="AUTHOR:%aN" --name-only
@@ -589,8 +581,8 @@ git -C <path> log origin/$DEFAULT --since="<start_date>T00:00:00" --format="%at|
 # Per-author commit counts
 git -C <path> shortlog origin/$DEFAULT --since="<start_date>T00:00:00" -sn --no-merges
 
-# PR numbers from commit messages
-git -C <path> log origin/$DEFAULT --since="<start_date>T00:00:00" --format="%s" | grep -oE '#[0-9]+' | sort -n | uniq
+# PR/MR numbers from commit messages (GitHub #NNN, GitLab !NNN)
+git -C <path> log origin/$DEFAULT --since="<start_date>T00:00:00" --format="%s" | grep -oE '[#!][0-9]+' | sort -t'#' -k1 | uniq
 ```
 
 For repos that fail (deleted paths, network errors): skip and note "N repos could not be reached."
@@ -668,7 +660,7 @@ align cleanly. Never truncate project names.
 ║  • [1-line description of second theme]
 ║  • [1-line description of third theme]
 ║
-║  Powered by gstack · github.com/garrytan/gstack
+║  Powered by gstack
 ╚═══════════════════════════════════════════════════════════════
 ```
 
@@ -797,7 +789,7 @@ Use the Write tool to save JSON to `~/.gstack/retros/global-${today}-${next}.jso
   "projects": [
     {
       "name": "gstack",
-      "remote": "https://github.com/garrytan/gstack",
+      "remote": "<detected from git remote get-url origin, normalized to HTTPS>",
       "commits": 47,
       "insertions": 3200,
       "deletions": 800,