docs: architecture, configuration, development and features describe Scribe as it is today

Milestone 544, step 6217 (follow-up to #1778, which rewrote features.md and
api-reference.md in July but left architecture.md and configuration.md alone).

- architecture.md, configuration.md, development.md: rewritten against the
  code. They still described Ollama, chat, SSE generation, voice, project
  summaries, image caching, Docker secrets that the compose files don't use,
  a raw-SQL migration convention the migrations no longer follow, a 27-entry
  migration list, CalVer YY.MM.DD.N tags and the removed infra/ files.
- features.md: adds what shipped since July (spikes, claims, moments, rule
  versions and verification, lessons, reply shapes, snippets and the shape
  ledger, forge integration, family canon, design systems, retrieval tuning)
  and corrects the Settings tabs and keyboard shortcuts (g g is the graph).
- api-reference.md: adds the endpoints for snippets, lessons, design
  systems, family canon, platforms, shared areas, retrieval, rule versions,
  relations and verification, forge connections, webhooks, scheduled
  backups and the newer plugin hooks.
- api-keys-and-mcp.md: Settings tab is "MCP Access"; a plugin install
  section; the tool-family table matches the tools that exist.
- design-system.md: the dated "decisions in progress" changelog (April
  PR log, chat/journal/calendar surfaces) becomes a short present-tense
  section; the stored design system is named as the authority.
- sso-oauth.md: the app is Scribe, not "Fabled Assistant".
- README: feature summary and doc table brought current.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Makefile

@@ -20,7 +20,7 @@ health:
 migrate:
 	docker compose exec app alembic upgrade head
 
-# --- Local dev (requires: pip install -e ".[dev]" and cd frontend && npm ci) ---
+# --- Local dev (requires: uv sync --extra dev and cd frontend && npm ci) ---
 
 lint:
 	ruff check src/