Architecture rework: fix protocol bugs, add origin-side cache, document spec

8-expert review identified 3 bugs in shipped code (Vary header hallucination,
fn/function wire key mismatch, max-age=0 defeating PSR) — all fixed with
tests updated across Python and TypeScript.

Added: manifest version field, affects validation, wire format convention,
origin-side cache module (HMAC key derivation, MemoryCache + RedisCache
backends, reverse index for scoped invalidation, executor integration).

16 known issues documented in cache/KNOWN_ISSUES.md from expert review —
critical items (user_id not passed, purge race condition, no Redis error
handling) to be fixed in follow-up.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

MIZAN.md

@@ -183,6 +183,12 @@ The cache identity for a context is: context name + shared elevated params.
 `user_id=123` is one cache entry. Per-function overrides via `specify` are
 part of the request but do not change the cache identity.
 
+### Wire format convention
+All parameter names on the wire (HTTP headers, JSON keys, query params, manifest fields)
+use `snake_case`. TypeScript adapters convert to `camelCase` at the boundary for local use
+but emit `snake_case` in protocol-level artifacts (invalidation headers, manifest params).
+This is a protocol rule, not a language convention.
+
 ---
 
 ## 4. Mutation Invalidation with `affects`