SPEC v0.5: M3 and M5 decisions (D-026 to D-034, D-040 to D-043), HANDOFF rewritten

Records the decisions proposed by M3 (503cee5) and M5 (c28c52b). M5's proposals
D-030 to D-033 are renumbered D-040 to D-043; D-035 to D-039 are reserved for M4.
Adds the D-027 clock-skew re-stamp rule, M5's contract requests for M8 (PLAN-M8,
SPEC 11.3), the connect-info note for M4 (PLAN-M4), the picture size note (PLAN-M6),
and updates prompts/README status.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

PLAN-M6.md

@@ -27,6 +27,7 @@ Implement `:core:design` from the approved `docs/ux/design-spec.md`: theme, colo
 - M2b created the module shell (build file, manifest, empty string files); M6 owns it and fills it in (D-004).
 - Screenshot goldens are committed; open every changed PNG before committing (CLAUDE.md).
 - `:core:design` depends only on `:core:model` (§6.2).
+- Avatars (v0.5, §14.2.4 readings): `:data` always loads pictures at size 512 (E-11); the 128 variant is unused. If the avatar component needs the small size, ask the orchestrator for a size parameter (a contract request on `:core:model` and `:data`).
 
 ## 4. Owned paths
 From SPEC §14.7, verbatim: `android/core/design/**` (owner M6; after landing: "M7x may not edit; requests go through the orchestrator").