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/src/nisse_dev/agent.py

@@ -33,7 +33,7 @@ from nisse_dev.tools import Workspace
 from nisse_dev.worker import SerialWorker
 
 # How long shutdown waits for running work before leaving the store to the
-# durability layer (A2/A3). A milestone can run far longer than a service
+# durability layer (L8). A milestone can run far longer than a service
 # manager allows for a stop, and a hard exit mid-work is already safe.
 SHUTDOWN_WAIT_S = 10.0
 
@@ -52,14 +52,14 @@ def discover_models(config: AgentConfig, oplog: OpLog) -> ModelCatalog:
     catalog = ModelCatalog.discover(config.llm_base_url, config.llm_token)
     catalog.validate(config.roles.pinned())
     # Every role's context window must be known before a request is built
-    # against it (A10): a guess that is too large reaches a server that may
+    # against it (L6): a guess that is too large reaches a server that may
     # silently cut the prompt.
     catalog.require_limits(config.roles.pinned())
     for role in TOOL_DRIVING_ROLES:
         facts = catalog.facts(config.roles.resolve(role))
         if facts.supports_tools is False:
             # A warning, not a refusal: models LiteLLM declares tool-less are
-            # observed driving tool loops anyway, and A15 expects weak local
+            # observed driving tool loops anyway, and L9 expects weak local
             # models to be accommodated rather than excluded.
             oplog.emit(
                 "model_tools_unsupported",
@@ -83,7 +83,7 @@ class Agent:
     _stopped: threading.Event
 
     def start(self) -> None:
-        """Boot in the order A3 requires: reconcile against external truth
+        """Boot in the order L8 requires: reconcile against external truth
         before accepting a single operator command."""
         self.worker.call(self.orchestrator.start)
         self.transport.start()
@@ -108,7 +108,7 @@ class Agent:
         try:
             self.worker.call(self.store.close, timeout=SHUTDOWN_WAIT_S)
         except TimeoutError:
-            pass  # still working; exiting mid-work is what A2/A3 are for
+            pass  # still working; exiting mid-work is what L8 are for
         self.worker.stop(timeout=SHUTDOWN_WAIT_S)
         self._stopped.set()
 
@@ -151,7 +151,7 @@ def make_llm_clients(
         )
     )
     # Delegations prefer the vendor-native route; fidelity is cheap
-    # elsewhere (A5). Which route a given model gets is decided by
+    # elsewhere (L9). Which route a given model gets is decided by
     # select_client, not by where the caller happens to sit.
     passthrough = budgeted(
         AnthropicPassthroughClient(