docs: rewrite README to the docs standard; polish docs/

README: verified quickstart (Docker builder, dry-run, live demo), mermaid
architecture, CLI/config/routing reference tables, status table from
REPORT.md, correct ukrrs repo URLs. docs/: Status front-matter lines on
all PORTING-NOTES (secrets notes now tracked). DESIGN: table of contents
with anchor links; sections untouched.

💘 Generated with Crush

Assisted-by: Crush:glm-5.2

docs/PORTING-NOTES-crush.md

@@ -4,6 +4,8 @@ Scope for MOPAC harness: MCP client, sessions/resume, provider routing,
 headless loop; OAuth deferred (LiteLLM key suffices). Paths relative to
 `reference/crush/`; line refs from study 2026-08-28, drift possible.
 
+Status: 2026-08-28 — complete; reference study, line refs may drift with upstream.
+
 ## 1. MCP plumbing
 
 Code in `internal/agent/tools/mcp/` (NOT `internal/client/` = daemon RPC).