test(mcp): prove tracedecay_configuration_protected_preview behavior

[ScriptedAlchemy]

Summary

• Prove tracedecay_configuration_protected_preview through the production MCP tools/call path.
• Repair the CI failures on the previous head: rustfmt, the privacy doc lint, the Codex prepare outcome when codex is absent, and the delivery credential-gate case.

Motivation

Callers of this tool need a dry-run that names the submitted change without leaking the protected value, and a typed refusal when the CAS revision or the change itself is not admissible.

The previous head's CI was red for reasons that also fail on origin/master: unformatted match chains, a rustdoc list that starts with a comma, a prepare test that demanded Ready when the Codex CLI is missing, and a credential-gate assertion that searched for lowercase configure.

Changes

• crates/tracedecay/src/daemon/production_harness/configuration_protected_preview_journey_test.rs drives the preview tool the way a host does.
• Formatting in lifecycle_lease.rs and the generation-store lock, the privacy RE2 doc comment, the Codex prepare expectation, and the delivery-gate phrase Configure a token.

Test plan

• scripts/require-exact-test.sh cargo test -p tracedecay --lib daemon::production_harness::configuration_protected_preview_journey_test::protected_preview_redacts_the_change_and_refuses_stale_or_invalid_input -- --exact — 1 passed; 0 failed in 1.67s
• cargo fmt --all -- --check
• cargo clippy -p tracedecay-privacy --lib -- -D warnings
• Codex prepare test and delivery credential-gate test, exact filters, 1 passed each
• Code-index scheduler tests and the legacy generation RSS probe still fail on origin/master the same way. Those assertions were not loosened.

Checklist

• CHANGELOG.md updated (under [Unreleased] if no version bump)
• No secrets, credentials, or .env files included
• Breaking changes documented (if any)

  

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[ScriptedAlchemy]

Review (as part of the 2026-09-18 PR sweep): not merging in this form. The journey test itself is well built, but the PR bundles:

• an unexplained production behaviour change in code_index_scheduler/serving.rs (text_artifact_admitted_build_budget reclassifies a refusal from AuthorityUnavailable to BudgetExceeded when used_bytes > 0 && host_capacity >= minimum_bytes), not mentioned in the body;
• two scheduler tests that gain serving_generation writes changing what generation the queries observe;
• weaker versions of two fixes master already carries (codex/tests.rs accepts Ready without asserting anything; delivery_api.rs assertion), plus stale digest churn that is byte-identical to master.

Suggested path: resubmit as two PRs off current master — (1) the journey test alone (production_harness.rs + configuration_protected_preview_journey_test.rs), (2) the BudgetExceeded reclassification as its own change with the reasoning and a test that pins it.

[ScriptedAlchemy]

Superseded: #1815 (folded into #1848, now on master 51990b1) proves the protected-preview journey; this branch is 11 commits behind and carries the older proof. Closing.