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/AGENTS_ADRS.md

@@ -0,0 +1,89 @@
+# Agent Instructions: Architecture Decision Records (ADRs)
+
+Architectural decisions live in **`agents-docs/adr/`** as numbered Markdown files (`NNNN-slug.md`).
+
+This document defines how agents must detect, document, and maintain architectural decisions as the codebase grows.
+
+> This file is part of the agent instruction infrastructure.
+> Do NOT create, delete, or modify this file unless explicitly instructed.
+
+---
+
+## What an ADR is
+
+A short record of an architectural decision that future engineers (and agents) will need context for. The format is Nygard short form:
+
+- Title and number (`ADR-NNNN: <slug>`).
+- Required: 1–3 sentences each covering **Context** (why this came up), **Decision** (what was chosen), and **Rationale** (why this option over alternatives).
+- Conventional: `Status` (usually `Accepted` for new ADRs; `Superseded by ADR-MMMM` once overturned).
+- Optional: `Considered Options`, `Consequences` — add only when they genuinely help. Most ADRs won't need them.
+
+See `agents-docs/adr/0001-record-architectural-decisions.md` for the canonical example — a minimal four-section ADR that matches the typical shape.
+
+The value is in recording **that a decision was made** and **why** — not in completing formal sections.
+
+---
+
+## ADR Contract (MANDATORY)
+
+### When to write an ADR
+
+The canonical criteria — the 3-criteria gate — live in `agents-docs/AGENT_WORKFLOW.md` § 5 ADR upkeep. Read those before writing. In short: write an ADR only when the decision is **hard to reverse**, **surprising without context**, and the **result of genuine trade-offs**. If any of the three is missing, don't.
+
+Suitable topics: architectural patterns, integration approaches, significant technology selections, scope boundaries, intentional deviations from standard practices, non-obvious rejections of alternatives.
+
+### Read before crossing decision boundaries
+
+Before non-trivial changes in an area, scan `agents-docs/adr/` for decisions that touch it. If your work would contradict an existing ADR:
+
+- **Surface it explicitly**, don't silently override. Phrase it as: "_Contradicts ADR-NNNN (slug) — but worth reopening because…_"
+- If the contradiction is intentional, write a new ADR that supersedes the old one (see below).
+
+### Write the ADR in the same turn as the decision
+
+When the 3-criteria gate is met, write the ADR before reporting the task done. The `AGENTS.md` completion checklist has a line for this; don't tick the box without it.
+
+### Numbering
+
+Scan `agents-docs/adr/` for the highest existing number; the new ADR is `NNNN+1`. Use 4-digit zero-padded numbers (`0001`, `0002`, …).
+
+Slugs are kebab-case and describe the decision concisely: `0042-postgres-for-write-model.md`, `0043-event-sourced-orders.md`.
+
+### Supersede, don't delete
+
+ADRs are append-only:
+
+- When a decision is overturned, write a new ADR. The old one stays.
+- Add `Superseded by ADR-NNNN` near the top of the old ADR.
+- Add `Supersedes ADR-MMMM` near the top of the new one.
+- Never delete or rewrite history.
+
+---
+
+## Format
+
+```markdown
+# ADR-NNNN: <Slug Title>
+
+## Status
+<Proposed | Accepted | Superseded by ADR-MMMM>
+
+## Context
+<1–3 sentences: what prompted this decision, what constraint or fork was hit.>
+
+## Decision
+<1–3 sentences: what was chosen, plainly stated.>
+
+## Rationale
+<1–3 sentences: why this option over the alternatives.>
+
+<!-- Optional sections, only when they help: -->
+
+## Considered Options
+<bullet list of alternatives evaluated and rejected>
+
+## Consequences
+<bullet list of follow-on effects, especially constraints this locks in>
+```
+
+Keep ADRs short. Three sentences per section beats three paragraphs.