docs: scaffold agent instruction tree

Add AGENTS.md, CLAUDE.md, and the agents-docs/ tree (workflow, lessons,
engineering standards, context map, ADR seed, feature template) plus a
domain-bearing CONTEXT.md for each of the six subdomains: toju-app,
electron, server, e2e, website, docs-site.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

agents-docs/LESSONS.md

@@ -0,0 +1,38 @@
+# Agent Lessons
+
+Durable rules for AI agents working on this project. Read this file at session start. Append to it when this session produces a correction worth remembering.
+
+## How to use this file
+
+**At session start:** scan the rules below. If any match the work you're about to do, apply them.
+
+**During the session:** if the user corrects you, reverts your edit, or re-prompts with the same instruction — that is a signal to record a lesson before closing the task. See the trigger list in `agents-docs/AGENT_WORKFLOW.md`.
+
+**Format of a lesson:** every entry uses the four-slot template below. Brevity matters — if you can't state the rule in one sentence, the lesson isn't sharp enough yet.
+
+```markdown
+### <short imperative title>
+
+- **Trigger:** what you were about to do that turned out wrong (one line, concrete enough to pattern-match against)
+- **Rule:** what to do instead (one sentence, imperative voice)
+- **Why:** the consequence of getting it wrong — past incident, hidden constraint, user preference
+- **Example:** one concrete instance, ideally a code or command snippet
+```
+
+**Keep lessons sharp.** Tag each rule with one or two tags in square brackets after the title (e.g. `[testing] [migrations]`) so future agents can grep for relevance. If a rule no longer applies, delete it — stale rules drown the real ones.
+
+---
+
+## Lessons
+
+### Verify lint exits 0 before claiming done [verification]
+
+- **Trigger:** about to report a task as complete after running tests but skipping ESLint.
+- **Rule:** run `npm run lint` from the repo root and confirm exit code 0 before any "done" claim.
+- **Why:** `npm run test` only runs the toju-app Vitest suite — it doesn't cover the server, Electron, or website packages. ESLint (flat config in `eslint.config.js`) is the universal check across every package; type-style violations slip through tests and break Gitea Workflows for the next agent.
+- **Example:** `npm run lint && echo OK` — only claim done after seeing `OK`. For Electron type errors specifically, also confirm `npm run build:electron` succeeds (it invokes `tsc -p tsconfig.electron.json`).
+
+<!--
+Add new lessons above this comment, newest at the top.
+Delete this example once the project has accumulated 2-3 real lessons.
+-->