Retire the old build spec, and point every reference at the architecture (M0.1)

Development Plan M0.1. Every section reference in code, tests, specs/,
the example config, the tuning guide, and the CLAUDE.md and README files
now cites docs/Architecture.md (P, L, D, O, X, Q) instead of the old
spec's A-H, and docs/Architecture-Build-Spec.md is deleted (git keeps
it). The plan's old-to-new table goes with it.

Mostly mechanical, with a per-site choice where one old section split:
A4 became L2 where it meant stop/abandon/the loop and L3 where it meant
approvals; A10 became L6 in the context-budget code and L7 elsewhere; B2
became D4 for outbound Gitea and publishing and D5 for review intake;
'A3 step N' became the matching step of L8's boot sequence. Comments
describing behaviour the architecture drops (planning always escalating,
thresholds tuned at an old build step) now describe the current code and
point at the Development Plan.

docs/Architecture.md gains one line the rewrite missed: intake outages
delay but never fail work (old B2), now in L5, where the poller and
Matrix code cite it.

Comments and docs only; no behaviour change.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

tests/integration/test_model_capability.py

@@ -1,9 +1,9 @@
-"""Capability matrix across models (spec Part H, A15).
+"""Capability matrix across models (architecture L9, Q).
 
-Part H says the thresholds that depend on local capability — A12's failure
-count, A14's consult budget, A15's manifest size — must be tuned "at
-build-order step 5 on the real hardware". This is the measurement that makes
-that possible, rather than reasoning about model strength from reputation.
+The thresholds that depend on local capability (L9: the failure count, the
+consult budget, the manifest size) are tuned on the real hardware. This is the
+measurement that makes that possible, rather than reasoning about model
+strength from reputation.
 
 What it measures is the thing that actually breaks: whether a model can hold
 the tool-call contract our loops depend on. llama3.2 could not — it returned
@@ -102,7 +102,7 @@ def test_model_answers_at_all(model: str, catalog: ModelCatalog, routes) -> None
 def test_model_holds_the_planner_contract(
     model: str, catalog: ModelCatalog, routes
 ) -> None:
-    """A4's gating is structural at the tool layer: a model that answers in
+    """L3's approvals are structural at the tool layer: a model that answers in
     prose cannot be gated, because there is no plan to approve."""
     normalized, passthrough = routes
     client = select_client(model, normalized, passthrough, catalog)
@@ -161,7 +161,7 @@ def test_model_round_trips_a_tool_result(
 def test_model_holds_the_prompt_level_json_contract(
     model: str, catalog: ModelCatalog, routes
 ) -> None:
-    """A14 contracts structured output at the prompt level because vendors
+    """L9 contracts structured output at the prompt level because vendors
     differ on JSON enforcement. This measures whether that holds per model."""
     normalized, passthrough = routes
     client = select_client(model, normalized, passthrough, catalog)