docs: add phased implementation plan and architecture decision records

Turns the design doc into an ordered, dependency-correct build plan (phases
0-9) with an exit criterion per phase, and records the twelve architectural
decisions it rests on as ADRs.

Decisions: single Rust binary with routed compose services; Streamable HTTP
only; per-agent bearer tokens with clientInfo as a display hint only; SQLite;
get_rules delivered via session gating; full-document rule delivery; project_id
from day one; enforcement tier scoped to Bridle-mediated actions; stable tool
list on upstream failure; OpenAI-compatible embeddings with model/dim guarding;
pattern RAG gated behind a spike; CLAUDE.md + AGENTS.md as v1 renderer targets.

Deviates from the design doc's original 1-8 ordering by moving the audit log
and multi-project schema into phase 1, building the admin API incrementally
rather than all at the Web Panel phase, downgrading vendor guardrail sourcing
to manual-first, and gating the pattern-example RAG behind a validation spike.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019RZerbsHGF9Ka3bKhCjJ9m

docs/adr/0001-single-binary-with-routed-services.md

@@ -0,0 +1,32 @@
+# ADR-0001: Single Rust binary with routed compose services
+
+**Status:** Accepted (2026-08-08)
+
+## Context
+
+The design doc's architecture diagram shows Rules, Memory, the Kanboard wrapper, and the Web Panel
+as separate boxes, which reads as four independent deployables communicating over HTTP. Bridle
+targets single-host, single-user deployment. Splitting hand-written components across processes at
+that scale buys nothing: it costs four ports, four health checks, four failure modes, and turns
+what would be function calls into network hops.
+
+## Decision
+
+All hand-written components compile into **one Rust binary** with internal modules: `mcp` (server
+and session handling), `rules`, `memory`, `proxy`, `admin`, and the Web Panel's served assets.
+Module boundaries stay clean enough that any module could be split into its own service later
+without redesign.
+
+Third-party and off-the-shelf services remain **separate Docker Compose containers** — Qdrant,
+Kanboard, the embedding server, and the existing Gitea MCP server — with all agent traffic to them
+routed through the binary.
+
+## Consequences
+
+- One deployable, one health check, one log stream, one thing to restart.
+- No Python sidecar: the memory module is Rust talking to Qdrant and to an OpenAI-compatible
+  embeddings endpoint over HTTP.
+- Compose profiles for bundled-versus-external services are unaffected — see the deployment section
+  of the design doc.
+- If Bridle ever outgrows single-host, the module boundaries are the seams to split along. This is
+  a deliberate deferral, not an oversight.