docs(prd): add gitleaks allow supervision

docs/prds/prd-new-gitleaks-inline-suppression-supervision.md

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+# PRD prd-new: Gitleaks inline suppression supervision
+
+- **Status:** Active
+- **Author:** codex
+- **Created:** 2026-06-10
+- **Issue:** #208
+
+## Summary
+
+Route every `# gitleaks:allow` inline suppression through the existing
+supervisor approval queue before git-gate forwards a push upstream. The
+annotation remains available for test fixtures and confirmed false positives,
+but it no longer lets an agent silently bypass the gate's secret scan.
+
+## Problem
+
+Gitleaks supports inline suppression comments. With the default behaviour,
+a pushed line that contains a secret-like value and `# gitleaks:allow` is
+ignored by gitleaks and accepted by git-gate. That is convenient for dummy
+credentials in tests, but it also gives an agent a one-line bypass for a real
+secret. Once the commit lands, the diff alone cannot prove whether the
+suppression was legitimate.
+
+## Goals / Success Criteria
+
+1. Git-gate continues to run the normal gitleaks scan for every incoming ref.
+2. After the normal scan passes, git-gate runs a second scan with
+   `--ignore-gitleaks-allow` and a JSON report so suppressed findings become
+   visible.
+3. If that second scan reports no suppressed findings, the push proceeds
+   unchanged.
+4. If it reports suppressed findings, git-gate creates a `gitleaks-allow`
+   supervisor proposal containing the ref, file path, line number, rule,
+   commit, and flagged line for each finding.
+5. The push proceeds only when the supervisor explicitly approves the
+   proposal; rejection, malformed responses, missing supervisor configuration,
+   and timeout all refuse the push.
+6. The supervisor TUI requires a reason when approving a `gitleaks-allow`
+   proposal, so the audit trail records whether the approval was for a test
+   fixture or a false positive.
+
+## Non-goals
+
+- Replacing gitleaks or changing the main secret-detection rule set.
+- Removing support for `# gitleaks:allow`.
+- Automatically classifying fixture files or false positives.
+- Adding new supervisor transport or authentication mechanisms.
+
+## Design
+
+### Git-gate flow
+
+`git_gate_render_hook()` emits a `supervise_gitleaks_allow` shell helper.
+For each incoming ref, git-gate first runs the existing gitleaks command. If
+that scan passes, it runs:
+
+```sh
+gitleaks git \
+  --log-opts="$log_opts" \
+  --no-banner \
+  --redact \
+  --ignore-gitleaks-allow \
+  --report-format=json \
+  --report-path="$report_file" \
+  --exit-code 0
+```
+
+The second pass keeps the push path non-interactive while producing a report
+of findings that would otherwise have been hidden by inline suppression.
+
+### Supervisor proposal
+
+When the JSON report contains findings, an embedded Python helper writes a
+proposal into `SUPERVISE_QUEUE_DIR` using the existing proposal schema. The
+proposal uses:
+
+- `tool: "gitleaks-allow"`
+- a text payload with the ref and each finding's file, line, rule, commit,
+  and redacted code line
+- a justification that tells the operator to approve only dummy test fixtures
+  or confirmed false positives
+
+Git-gate then waits for `<proposal-id>.response.json` for
+`SUPERVISE_GITLEAKS_ALLOW_TIMEOUT_SECONDS`, defaulting to 300 seconds.
+`approved` and `modified` responses allow the push; `rejected`, invalid
+responses, invalid timeout configuration, or timeout refuse it.
+
+### Supervisor UI
+
+`TOOL_GITLEAKS_ALLOW` is added to the supervisor tool registry. The curses
+supervisor renders the proposal as text and allows approval or rejection.
+Modification is unavailable for this proposal type because there is no file
+patch to apply. Approval from the TUI prompts for a non-empty reason and
+writes that reason to the response/audit path.
+
+### Tests
+
+Unit tests assert that the rendered git-gate hook includes the second gitleaks
+pass, supervisor queue fields, and fail-closed messages. Supervisor tests cover
+the new tool constant, proposal archiving, and the required TUI approval
+reason.