feat: GStack Learns — per-project self-learning infrastructure (v0.13.4.0) (#622)

* feat: learnings + confidence resolvers — cross-skill memory infrastructure

Three new resolvers for the self-learning system:
- LEARNINGS_SEARCH: tells skills to load prior learnings before analysis
- LEARNINGS_LOG: tells skills to capture discoveries after completing work
- CONFIDENCE_CALIBRATION: adds 1-10 confidence scoring to all review findings

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

* feat: learnings bin scripts — append-only JSONL read/write

gstack-learnings-log: validates JSON, auto-injects timestamp, appends to
~/.gstack/projects/$SLUG/learnings.jsonl. Append-only (no mutation).

gstack-learnings-search: reads/filters/dedupes learnings with confidence
decay (observed/inferred lose 1pt/30d), cross-project discovery, and
"latest winner" resolution per key+type.

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

* feat: learnings count in preamble output

Every skill now prints "LEARNINGS: N entries loaded" during preamble,
making the compounding loop visible to the user.

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

* feat: integrate learnings + confidence into 9 skill templates

Add {{LEARNINGS_SEARCH}}, {{LEARNINGS_LOG}}, and {{CONFIDENCE_CALIBRATION}}
placeholders to review, ship, plan-eng-review, plan-ceo-review, office-hours,
investigate, retro, and cso templates. Regenerated all SKILL.md files.

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

* feat: /learn skill — manage project learnings

New skill for reviewing, searching, pruning, and exporting what gstack
has learned across sessions. Commands: /learn, /learn search, /learn prune,
/learn export, /learn stats, /learn add.

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

* docs: self-learning roadmap — 5-release design doc

Covers: R1 GStack Learns (v0.14), R2 Review Army (v0.15), R3 Smart Ceremony
(v0.16), R4 /autoship (v0.17), R5 Studio (v0.18). Inspired by Compound
Engineering, adapted to GStack's architecture.

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

* test: learnings bin script unit tests — 13 tests, free

Tests gstack-learnings-log (valid/invalid JSON, timestamp injection,
append-only) and gstack-learnings-search (dedup, type/query/limit filters,
confidence decay, user-stated no-decay, malformed JSONL skip).

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

* chore: bump version and changelog (v0.13.4.0)

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

* test: learnings resolver + bin script edge case tests — 21 new tests, free

Adds gen-skill-docs coverage for LEARNINGS_SEARCH, LEARNINGS_LOG, and
CONFIDENCE_CALIBRATION resolvers. Adds bin script edge cases: timestamp
preservation, special characters, files array, sort order, type grouping,
combined filtering, missing fields, confidence floor at 0.

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

* fix: sync package.json version with VERSION file (0.13.4.0)

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

* chore: gitignore .factory/ — generated output, not source

Same pattern as .claude/skills/ and .agents/. These SKILL.md files are
generated from .tmpl templates by gen:skill-docs --host factory.

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

* test: /learn E2E — seed 3 learnings, verify agent surfaces them

Seeds N+1 query pattern, stale cache pitfall, and rubocop preference
into learnings.jsonl, then runs /learn and checks that at least 2/3
appear in the agent's output. Gate tier, ~$0.25/run.

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

---------

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

CHANGELOG.md

@@ -1,5 +1,20 @@
 # Changelog
 
+## [0.13.6.0] - 2026-03-29 — GStack Learns
+
+Every session now makes the next one smarter. gstack remembers patterns, pitfalls, and preferences across sessions and uses them to improve every review, plan, debug, and ship. The more you use it, the better it gets on your codebase.
+
+### Added
+
+- **Project learnings system.** gstack automatically captures patterns and pitfalls it discovers during /review, /ship, /investigate, and other skills. Stored per-project at `~/.gstack/projects/{slug}/learnings.jsonl`. Append-only, Supabase-compatible schema.
+- **`/learn` skill.** Review what gstack has learned (`/learn`), search (`/learn search auth`), prune stale entries (`/learn prune`), export to markdown (`/learn export`), or check stats (`/learn stats`). Manually add learnings with `/learn add`.
+- **Confidence calibration.** Every review finding now includes a confidence score (1-10). High-confidence findings (7+) show normally, medium (5-6) show with a caveat, low (<5) are suppressed. No more crying wolf.
+- **"Learning applied" callouts.** When a review finding matches a past learning, gstack displays it: "Prior learning applied: [pattern] (confidence 8/10, from 2026-03-15)". You can see the compounding in action.
+- **Cross-project discovery.** gstack can search learnings from your other projects for matching patterns. Opt-in, with a one-time AskUserQuestion for consent. Stays local to your machine.
+- **Confidence decay.** Observed and inferred learnings lose 1 confidence point per 30 days. User-stated preferences never decay. A good pattern is a good pattern forever, but uncertain observations fade.
+- **Learnings count in preamble.** Every skill now shows "LEARNINGS: N entries loaded" during startup.
+- **5-release roadmap design doc.** `docs/designs/SELF_LEARNING_V0.md` maps the path from R1 (GStack Learns) through R4 (/autoship, one-command full feature) to R5 (Studio).
+
 ## [0.13.5.1] - 2026-03-29 — Gitignore .factory
 
 ### Changed