feat: Enhance project memory and skills documentation; add memory-sync skill for knowledge consolidation

CLAUDE.md

@@ -36,6 +36,7 @@ docs/
   ARCHITECTURE.md      # the three-context system and boundaries
   DECISIONS.md         # ADRs: BYO-key, inline styles, no shadow DOM, key story, Gitea CI
   TASKS.md             # active contracts derived from RECOMMENDATIONS.md
+  MEMORY.md            # curated durable knowledge; loaded every session; capped (60 lines)
   EVALS.md             # standing gates + failure-derived checks
   LESSONS_LEARNED.md   # codebase invariants (detail behind the ## Lessons list)
   HANDOFF.md           # current state, risks, next action
@@ -73,7 +74,7 @@ npm run test:e2e     # Playwright (requires a prior `npm run build`)
 npm run typecheck    # tsc --noEmit
 ```
 
-**Prerequisite:** Node. CI pins **Node 22** (`node:22-bookworm`). Run `npm install` before any `npm run *` — the binaries (`tsc`, `vitest`) come from `node_modules/.bin`.
+**Prerequisite:** Node. CI pins **Node 22** (`node:22-bookworm`). Run `npm install` before any `npm run *` — the binaries (`tsc`, `vitest`) come from `node_modules/.bin`. Install triggers `postinstall: wxt prepare`, which generates `.wxt/types/` — **typecheck fails without it** (`import.meta.env` is typed there). If a fresh clone errors with `Property 'env' does not exist on type 'ImportMeta'`, run `npx wxt prepare`.
 
 **Load unpacked in Chrome:** `npm run build` → `chrome://extensions` → Developer Mode → Load unpacked → select `.output/chrome-mv3`.
 
@@ -138,7 +139,7 @@ Workflows live in `.gitea/workflows/`:
 
 For coordinated work, run Fable as the main session (`claude --agent fable-orchestrator`) and let it route to specialists; see `.claude/AGENTS.md` for the roster. For LexAI code (`entrypoints/`, `src/`), prefer the **`lexai-extension-dev`** specialist over the generic `builder` — it knows the message contract, snapshot pattern, and key rules. Security-relevant changes (permissions, key path, dependencies) go through `security-auditor`.
 
-On-demand skills in `.claude/skills/`: `resume-project`, `continuous-improvement`, `dev-loop`, `attack-surface`, `prompt-injection-audit`, `self-model-audit`. Invoke by name; keep each run bounded.
+On-demand skills in `.claude/skills/`: `resume-project`, `memory-sync`, `continuous-improvement`, `dev-loop`, `attack-surface`, `prompt-injection-audit`, `self-model-audit`. Invoke by name; keep each run bounded.
 
 ## Quality gates by risk
 
@@ -168,8 +169,22 @@ Codebase invariants that break silently when violated (detail + evidence in `doc
 - Bump `version` in both `package.json` and `wxt.config.ts`.
 - Style inline; Tailwind classes do nothing until PostCSS is wired.
 
+## Memory protocol
+
+Project knowledge lives in layers; write each item to exactly one and link instead of duplicating:
+
+| Layer | Holds | Written when |
+| --- | --- | --- |
+| `docs/MEMORY.md` | durable facts, conventions, environment quirks, key paths | a fresh agent would waste tokens rediscovering it |
+| `docs/HANDOFF.md` | current state and next action only | end of every substantial task |
+| `docs/DECISIONS.md` | why a choice was made | a hard-to-reverse choice is made |
+| `docs/LESSONS_LEARNED.md` + `## Lessons` | verified mistakes and their preventions | a learning signal is verified |
+
+**Context budget caps** (session-start files are a recurring token tax): `## Lessons` ≤ 12 rules, `docs/MEMORY.md` ≤ 60 entry lines, `docs/HANDOFF.md` ≤ 25 lines, `docs/TASKS.md` Active ≤ 7 contracts. When a cap is hit, run `/memory-sync` to consolidate/archive before adding — never grow past the cap.
+
 ## State continuity
 
 - On a fresh/compacted/interrupted session, invoke `/resume-project` before planning or editing.
-- Before ending a substantial task, update `docs/HANDOFF.md` (verified state, changed paths, checks, risks, next action).
+- Before ending a substantial task, update `docs/HANDOFF.md` (verified state, changed paths, checks, risks, next action) and promote any durable new knowledge into `docs/MEMORY.md` per the memory protocol.
+- Run `/memory-sync` at a phase change, before ending a long run, or when a capped file is full.
 - After a verified recurring mistake or workflow gap, invoke `/continuous-improvement`; durable agent/skill changes go through `system-steward`.