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.example.yaml

@@ -12,7 +12,7 @@ state_db: ~/nisse-demo-workspace/state.db
 workspace: ~/nisse-demo-workspace/project  # the clone
 project: demo
 
-llm:                                  # A5: LiteLLM is the only LLM destination
+llm:                                  # L9: LiteLLM is the only LLM destination
   base_url: http://litellm.example:4000
   token: ${NISSE_LLM_TOKEN}
   # Ceiling on each response. The model's own max_output_tokens in LiteLLM
@@ -22,20 +22,20 @@ llm:                                  # A5: LiteLLM is the only LLM destination
   # hung connection; slow local models can take minutes over a long answer.
   request_timeout_s: 600
 
-roles:                                # A11: role -> LiteLLM model alias
+roles:                                # L9: role -> LiteLLM model alias
   executor: qwen3.8-27b         # the local tier: best executor in the benchmark (PR #55)
   planner: claude-opus-5-5      # high-end judgement: plans a weaker executor follows
   delegate: claude-opus-5-5     # takes over what the executor got stuck on
   consultant: claude-haiku-4-5  # one question at a time, no tools: cheap is enough
 
-matrix:                               # A1
+matrix:                               # L5
   homeserver: https://matrix.example
   user_id: "@nisse-dev:example"
   token: ${NISSE_MATRIX_TOKEN}
   room_id: "!roomid:example"
   operators: ["@you:example"]
 
-gitea:                                # B2
+gitea:                                # D4, D5
   url: https://gitea.example
   token: ${NISSE_GITEA_TOKEN}
   repo: owner/demo-repo
@@ -48,10 +48,10 @@ gitea:                                # B2
 tuning:
   executor:
     max_turns: 40            # model calls per milestone before it stops as capped
-    failure_limit: 2         # consecutive failed commands before escalating (A12)
+    failure_limit: 2         # consecutive failed commands before escalating (L9)
   expert:
-    consult_budget: 3        # ask_expert calls per milestone (A14)
-  delegation:                # hard caps on one delegation (A13)
+    consult_budget: 3        # ask_expert calls per milestone (L9)
+  delegation:                # hard caps on one delegation (L9)
     max_turns: 30
     max_tokens: 200000
     wall_clock_s: 900