test(opencode): isolate the custody log sink from the live state file

[iceteaSA]

What was wrong

The plugin's hermetic test suite writes into the operator's live telemetry file.

Measured on the deployment that runs this plugin: ~/.local/state/cortexkit/opencode-plugin/custody.jsonl held 2473 rows, and 1989 of them (80%) came from 435 PIDs that lived under two seconds, one per bun test run. One example: pid 793109 wrote nine rows in 40ms, one second after a gate run started, with states serving, transient/transport_error, CustodyExhaustionError, served, timeout, gone for provider deepseek. Read cold, the file describes a deepseek not-found incident that never happened.

Mechanism: plugin.ts falls through to the default file sink when a test constructs a plugin or serve closure without injecting a logger (createLogger(dependencies.logSink ?? ...)). serve.test.ts builds eight and injects a logger into five; freshness.test.ts ten and eight. The default sink is the real state path.

Change

Two layers, on purpose. Injecting a logger into each existing test fixes the tests that exist; the next test that forgets is the one that matters.

• packages/opencode/src/tests/preload.ts, wired from a root bunfig.toml and a package bunfig.toml (root-invoked bun test packages/... does not pick up the package file; verified both invocation shapes print the guarded env): sets CLAUSTRUM_CUSTODY_LOG=off unless a test set it explicitly, and points XDG_STATE_HOME at a fresh mkdtemp directory so even a test that sets a state-relative path cannot reach the real one.
• Root package.json test:hermetic gains CLAUSTRUM_CUSTODY_LOG=off beside the two existing isolation vars, so the gate path is isolated even if bunfig resolution changes.
• sink-isolation.test.ts: builds a serve closure with no logger, drives one serve, and asserts the $HOME-derived live path gained nothing (existence, content, mtime).

Verification

The arrival proof, run by me on the live file as the oracle. Defeating layer 1 alone (CLAUSTRUM_CUSTODY_LOG= empty) is absorbed by layer 2 and stays green, which is the design working, not the test failing to discriminate. The discriminating mutation is disarming the preload itself:

preload.ts replaced with a comment (0 env assignments)
  0 pass 1 fail · live rows 2512 -> 2515 (+3)
preload.ts restored byte-identically (cmp)
  1 pass 0 fail · live rows unchanged

Those three rows are the last fixture rows that file will receive from this suite.

bun run test:hermetic: 230 pass, 0 fail. bash scripts/gate.sh: exit 0. Five files, 84 insertions, 1 deletion, all in the test harness; no source change.

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}

---

Summary by cubic

Stops the opencode plugin's hermetic tests from writing into the operator's live custody log. Tests previously produced 80% of the rows in ~/.local/state/cortexkit/opencode-plugin/custody.jsonl — including a phantom deepseek not-found incident — because a plugin built without an injected logger falls through to the real file sink.

Bug Fixes

• A preload, wired from both bunfig.toml files, sets CLAUSTRUM_CUSTODY_LOG=off unless a test sets it and redirects XDG_STATE_HOME to a fresh temp directory so state-relative paths can't reach the live file.
• The test:hermetic script gains the same env override so the gate stays isolated even if bunfig resolution changes.
• sink-isolation.test.ts builds a logger-less plugin, serves once, and asserts the live path is unchanged; removing the preload makes it fail and writes 3 rows to the live file, proving it discriminates.
• No source changes — the diff is confined to the test harness and scripts.

^{Written for commit e8b9a24. Summary will update on new commits.}