[ve] Déjà Code rules, utility extractions & test coverage

[paullewis]

What

Introduces the Déjà Code pattern — detecting repeated multi-statement code and
paving it with shared utilities + ESLint rules. Also adds unit tests for the
previously untested app-screen.ts progress engine and fixes two typos.

Why

Two independent 20-line blocks in create-chiclets.ts and
create-truncated-value.ts implemented identical LLM content summarization
logic, and layout-graph.ts had an inline groupBy that duplicated a common
pattern. Extracting these into shared utilities with enforcing ESLint rules
prevents the patterns from drifting back. The app-screen.ts module powers all
progress bars but had zero direct unit tests.

Changes

Déjà Code infrastructure

• .agent/README.md — new agent practices index
• .agent/deja-code.md — Déjà Code concept docs
• .agent/workflows/deja-code.md — slash-command workflow
• .agent/rules/breadboard.md — updated memory rules
• eslint.config.js — register two new deja-code-* rules

Utility extractions + ESLint rules

• src/utils/summarize-llm-content.ts [NEW] — extracted LLM content
  summarization
• eslint-rules/deja-code-prefer-summarize-llm-content.js [NEW] — enforces
  usage
• src/utils/group-by.ts [NEW] — extracted generic groupBy
• eslint-rules/deja-code-prefer-group-by.js [NEW] — enforces usage
• create-chiclets.ts, create-truncated-value.ts — refactored to use
  summarizeLLMContentValue
• layout-graph.ts — refactored to use groupBy

Tests

• tests/utils/summarize-llm-content.test.ts [NEW] — tests for the
  extraction
• tests/utils/group-by.test.ts [NEW] — tests for groupBy
• tests/sca/utils/app-screen.test.ts [NEW] — 20 tests for
  createAppScreen, setScreenDuration, tickScreenProgress

Bug fixes

• decode-error.ts — "volate" → "violate" (user-facing error copy)
• serialization.ts — "Serilialized" → "Serialized" (internal types)

Testing

• node --test dist/tsc/tests/sca/utils/app-screen.test.js — 20/20 pass
• node --test dist/tsc/tests/utils/group-by.test.js — verify groupBy tests
  pass
• node --test dist/tsc/tests/utils/summarize-llm-content.test.js — verify
  summarize tests pass
• ESLint: run npx eslint to verify new rules flag inline patterns

[github-actions]

📊 Coverage Report

Metric	PR	Main	Delta
Lines	98.23%	98.15%	🟢 +0.08%
Functions	98.17%	98.10%	🟢 +0.07%
Branches	94.32%	94.29%	🟢 +0.03%

🌟 More lines covered than before.