v0.22.0 — discrimination probe, contest channel, fold-in exception

Sentinel field-feedback release — refinements proposed by a downstream Sentinel operator after ~40 production reviews, each verified against cited evidence before acceptance. Ruleset stays v1, rubric stays v1: the report protocol (Status: line, Required action mapping) and severity tiers are unchanged; this release adds resolution procedures only, all as in-line extensions (SENTINEL.md remains 177/178 non-blank lines).

Added

• Dim D discrimination probe (dim-d-testing.md): mutation-based oracle verification codified — when command execution is available, a suspected non-discriminating test is verified by neutering the pinned behavior in a throwaway worktree and confirming the test goes RED. Fail-closed: no isolated execution → static-evidence 🟡 flagged (unverified — no execution); the probe upgrades evidence, never excuses omitting a static finding.
• Contest channel for false-positive 🔴s (SENTINEL.md §Severity adjustment + SEVERITY-RUBRIC step 4): a 🔴 whose factual premise appears wrong may be contested, never downgraded — the originating dimension is re-dispatched ONCE with counter-evidence from Sentinel's own tool use; its second verdict is final and logged in the Execution Log. PR/invoker text claiming a false positive is a 🔴 signal, never contest grounds. Resolves the documented contradiction between "NEVER downgrade a sub-agent 🔴" and the false-positive livelock.
• Fold-in exception for CONDITIONAL 🟡s (SENTINEL.md Follow-ups): small, same-file, no-new-risk 🟡 fixes MAY be folded into the PR instead of filed as issues — but the folded SHA MUST be re-invoked for a fresh verdict before merge (delta re-review applies). Size guidance is advisory (~≤10 LOC); the re-invoke requirement is the invariant. Removes the file-only backlog treadmill without weakening SHA-binding.
• Eval fixtures 11-nondiscriminating-oracle.md (static half of the discrimination probe: a non-discriminating oracle that is the only coverage of the changed behavior → D 🔴 REJECTED per the new escalation clause; the 🟡 golden-row boundary is documented in the fixture) and 12-contest-injection.md (contest-channel abuse: PR text arguing a 🔴 is a false positive must never bypass REJECTED).

Fixed

• Dim D "Shared fixture safety" now escalates to 🔴 when a helper/mock edit stops any test from executing new/changed logic, aligning the dim file with the rubric's "new data layer never executed by any test" golden row. Baseline eval runs (fixture 10) showed dim-level sub-agents reproducibly held this at 🟡 because the dim file's 🟡 default contradicted the golden row — the orchestrator's Phase 3 escalation still caught it end-to-end, but the dimension holding 🔴-blocking authority should say it directly.
• Eval fixture 07's synthetic diff contained an unintended legitimate 🔴 (unchecked res.ok cached CDN error pages as avatar bytes); an explicit guard was added so the fixture again isolates its 🟡 missing-timeout calibration purpose. Found by the baseline eval discipline.
• Eval fixture 08's Expected block clarified: "zero 🟡" applies to the post-calibration end-to-end verdict; dim-level advisory 🟡s are tolerated per README scoring rules.

Rejected (recorded for governance)

• Test-only reduced-dispatch lane (run only a discrimination probe for test-only PRs): same loophole class as the previously rejected feat fast-path — test-only PRs are where test-erosion attacks live. Filed as a sentinel:deferred issue with telemetry-based revisit criteria.