Structural only — no behavior change. Introduces:
- PromptAssembly: named 3-region wrapper around build_prompt_messages()
with to_messages(), immutable_prefix, appendable_log, volatile_scratch,
total_bytes, estimated_tokens.
- CacheMetrics: per-session cache-hit tracking with hit_rate() and
record().
- Session::build_prompt_assembly() wraps existing build_prompt_messages()
with no logic change.
- 5 golden tests: assembly structure, empty volatile, hit rate
calculations, record accumulation.
- Linked T1.4-PROMPT-DISCIPLINE-PLAN.md from COLIBRI-CUTOVER-PLAN.md.
No trimming, no escalation, no scheduler changes — PR 2 and 3 follow.
Parked branches (colibri-skills, zot harness) untouched.
Build: pass | Tests: 41/41 green (+5 new) | Clippy: clean | Fmt: clean
Sam & Hermes
7c1a9d886a