docs(P-036): address Codex review — SCC-level cache keys, span re-projection

Two P2 review points on the "Incrementality and caching" section, both
accepted:

- Recursive SCCs: per-method keys that embed callee summary hashes are
  circular inside a recursive component (A's key needs B's cached summary and
  vice versa). The cacheable unit for a recursive component is now the SCC
  itself, keyed by the members' local inputs plus dependencies OUTSIDE the
  component — reconstructible bottom-up over the acyclic condensation.
  Cross-member hashes are validated after load, never used for lookup.

- Evidence spans: a semantic body hash survives pure line movement while
  cached spans go stale. Cache hits reuse semantic effects and evidence
  structure only; spans are re-projected from current frontend facts at
  diagnostic time (the existing "formatting is a projection" rule), i.e. a
  cached span is valid only with the source-map version it was minted against.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015de4MezSeUnZBoWq1fFU5M

Author: claude

docs/proposals/P-036-interprocedural-semantic-architecture.md

@@ -627,6 +627,27 @@ callee summary dependency hashes
 configuration/profile hash
 ```
 
+Two consequences of that key shape must be designed in rather than discovered
+in production:
+
+- **Recursive SCCs cache at SCC granularity.** Inside a recursive component,
+  each member's callee dependency hashes include the other members, so
+  per-method keys cannot be reconstructed before some entry is retrieved. The
+  cacheable unit for a recursive component is the SCC itself: its key derives
+  from the members' local inputs (body hashes, signatures, domain/config
+  versions) plus the dependency hashes of summaries *outside* the component —
+  all reconstructible bottom-up over the acyclic condensation. Per-method
+  entries inside the component stay locally addressable; their cross-member
+  dependency hashes are validated after loading, never used for lookup.
+- **Evidence spans are a projection, not cached truth.** A semantic body hash
+  deliberately survives edits that only move code (inserting lines above an
+  otherwise unchanged method), but source spans captured in cached evidence do
+  not. A cache hit may reuse semantic effects and evidence *structure* (stable
+  IDs and edges); the spans rendered to users are re-projected from the current
+  frontend facts at diagnostic time — the same "formatting is a projection"
+  rule the evidence section imposes. Equivalently: a cached span is valid only
+  together with the source-map version it was minted against.
+
 Changing a leaf method invalidates:
 
 1. its local CFG/summary;