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

nisse-dev/tests/test_agent_build.py

@@ -137,8 +137,8 @@ def test_the_whole_graph_assembles(tmp_path: Path, origin: Path, monkeypatch) ->
     assert orchestrator._board is not None
     assert orchestrator._delegate is not None
     assert orchestrator._poller_factory is not None
-    assert orchestrator._executor._delegate is not None  # A12 escalation path
-    assert orchestrator._executor._expert is not None  # A14 consult path
+    assert orchestrator._executor._delegate is not None  # L9 escalation path
+    assert orchestrator._executor._expert is not None  # L9 consult path
     agent.stop()
 
 
@@ -181,7 +181,7 @@ def test_poller_factory_ignores_the_agents_own_comments(
 def test_delegation_uses_the_passthrough_route(
     tmp_path: Path, origin: Path, monkeypatch
 ) -> None:
-    # A13: delegations run vendor-native; the normalized route is for the
+    # L9: delegations run vendor-native; the normalized route is for the
     # places where fidelity is cheap.
     from nisse_dev.llm import AnthropicPassthroughClient, LiteLLMClient
 
@@ -203,7 +203,7 @@ def test_httpx_clients_are_not_shared_between_routes(
     agent.stop()
 
 
-# --- startup model discovery (A5/A11) ------------------------------------
+# --- startup model discovery (L9) ------------------------------------
 
 
 def test_a_typod_role_refuses_to_boot(tmp_path: Path, monkeypatch) -> None:
@@ -233,7 +233,7 @@ def test_a_role_this_key_cannot_reach_refuses_to_boot(
 
 
 def test_a_tool_less_model_warns_but_still_boots(tmp_path: Path, monkeypatch) -> None:
-    # A15 expects weak local models to be accommodated, and models LiteLLM
+    # L9 expects weak local models to be accommodated, and models LiteLLM
     # declares tool-less are observed driving tool loops anyway.
     import io
 
@@ -285,7 +285,7 @@ def test_the_resolved_model_is_pinned_at_task_start(
 def test_delegation_records_what_the_alias_resolved_to(
     tmp_path: Path, origin: Path, monkeypatch
 ) -> None:
-    # A16 eval history keyed on an alias alone would average across whatever
+    # L9 eval history keyed on an alias alone would average across whatever
     # that alias pointed at over time.
     agent = build_offline(tmp_path, origin, monkeypatch)
     assert agent.orchestrator._delegate._backing_model == "anthropic/claude-opus-5"