T09: crystallization

A stable agentic realization becomes deterministic code. All four exit
criteria met; 163 tests pass.

- crystallization.py: trajectory capture, stability assessment requiring the
  same path across several runs, CrystallizedDriver, pytest codegen
- crystallized/test_grant_access.py: generated, runs with no model, carries
  its lineage in the docstring
- descendant preserves the ancestor's oracle set, agrees with it across five
  lab versions, and still catches a seeded defect
- reversibility shown both ways via new M24 (grant endpoint renamed): the
  frozen descendant fails loudly rather than searching, and the agentic
  ancestor recovers from the same mutation

F-0007 (open): the 54% cost reduction must not be quoted in support of the
thesis. The T07 runtime is token-free, so the measured saving is one page
fetch, one parse and a two-candidate scoring pass. The saving the concept
actually claims - tokens, latency, retry variance - is unmeasured. Together
with F-0005 this makes a bounded live-model experiment the highest-value next
investment.

Assertions in the generated test are imported rather than restated, so it is
not fully standalone. Deliberate: paraphrased claims would be a second
unverified statement of intent.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Assistant: claude-code
Assistant-Model: opus
Assistant-Process: 1629012@bnt-lap001
Assistant-Session: 78d4fb13-8a1e-474b-87a3-9b9261c49a39

workplans/TD-WP-0002-vertical-spike-crystallization.md

@@ -415,7 +415,7 @@ without a human, so the safety result is not bought by escalating everything.
 
 ```task
 id: TD-WP-0002-T09
-status: todo
+status: done
 priority: high
 state_hub_task_id: "855a1f41-b839-57fc-87b8-198ce2a9f6b1"
 ```
@@ -432,6 +432,31 @@ Exit: the generated test runs with zero agentic involvement, preserves the
 relevant claims and oracles, retains visible lineage, and measurably costs less
 to execute than the agentic ancestor.
 
+**Done 2026-08-23.** `crystallization.py`, `crystallized/test_grant_access.py`
+(generated), 163 tests pass. All four exit criteria met.
+
+- Freezing requires the **same** path across several runs, not one success. One
+  run proves the agent can find a way; it does not show the surface has stopped
+  moving, and freezing on a single observation is how a crystallized test becomes
+  flaky the first time a page renders differently.
+- **Reversibility demonstrated in both directions.** M24 (grant endpoint renamed)
+  breaks the frozen path; the descendant fails *loudly* rather than falling back
+  to searching — falling back would quietly turn a T5 asset into a T1 one and
+  hide the signal crystallization exists to produce — while the agentic ancestor
+  recovers from the same mutation. That is what distinguishes crystallization
+  from ordinary codegen: the agentic form is not discarded.
+- **F-0007 (open) — the economic case is unmeasurable.** The descendant is 54%
+  cheaper, and that number should not be quoted in support of the thesis. The
+  T07 runtime consumes zero tokens, so the entire saving is one page fetch, one
+  parse and a two-candidate scoring pass. The saving crystallization actually
+  claims — model tokens, latency, retry variance — is two or three orders of
+  magnitude larger and entirely absent from this measurement.
+- The generated test is **not fully standalone**: realization is plain `urllib`,
+  but assertions are *imported* rather than restated, because a generated test
+  that paraphrases its claims creates a second unverified statement of intent.
+  Right call, and it qualifies the "drops into existing CI" story — what drops in
+  is the realization; the claims still need the use-case module.
+
 ## Gate review and first compression pass
 
 ```task