feat(project): enrich repo constitution (invariants, branch policy, escalation)

Per the layered-authority clarification (base myth → global Constitution → repo
constitution = local law → task packet → runtime policy), extend
.codewhale/constitution.json beyond authority+verification with optional:

- protected_invariants — repo invariants the agent must not break
- branch_policy — branch/release policy in effect
- escalate_when — conditions to stop and escalate to the user

All optional; rendered as concise model-facing prose. The global Brother Whale
identity anchor and Constitution in prompts/base.md are unchanged (verified
untouched on this branch). Dogfood constitution.json filled with CodeWhale's
real invariants (prefix-cache byte-stability, transcript replay, stable Rust,
cli/tui parity), branch policy (codex/v0.8.53), and escalation rules. Docs note
the layered hierarchy.

cargo test -p codewhale-tui --bins → 3946 passed; clippy clean.

.codewhale/constitution.json

@@ -8,11 +8,23 @@
     "memory",
     "previous-session handoffs"
   ],
+  "protected_invariants": [
+    "Keep the active first-turn tool-catalog head byte-stable (DeepSeek KV prefix-cache invariant); changes to it must be one-time and deterministic.",
+    "Preserve old-session transcript replay: never remove a tool's registration just because it is deprecated/hidden.",
+    "Stable Rust only (edition 2024); no nightly features.",
+    "Keep the codewhale CLI dispatcher and the codewhale-tui binary in sync when crates/tui changes."
+  ],
+  "branch_policy": "v0.8.53 work targets the codex/v0.8.53 integration branch, not main. One PR per logical workstream; do not mix unrelated fixes.",
   "verification_policy": {
     "before_claiming_done": [
       "run the focused tests for the changed crate (cargo test -p <crate>), then cargo check/clippy as appropriate",
       "read changed files back to confirm the edit landed as intended",
       "never claim verification you did not perform"
     ]
-  }
+  },
+  "escalate_when": [
+    "an action is destructive or hard to reverse and was not explicitly authorized",
+    "changing provider/auth/config or anything that sends data to an external service",
+    "deleting or overwriting files you did not create, or that contradict how they were described"
+  ]
 }