fix(installer): harden greenfield detector contracts

docs/scratchpads/1050-install-state-machine-red-fixture.md

@@ -50,7 +50,7 @@ Implement C1 from the canonical greenfield-install PRD v2: a transactional P0–
 - [x] Corrected RED transcript captured and reported, including the git-present/absent controls and strict P3 PASS.
 - [x] State-machine implementation complete: private pre-mutation journal/snapshot, P0–P8 `--check`, P2–P8 fault seam, rollback, durable manifest/journal seal, action-status persistence, safe rollback roots, and stale-projection recovery.
 - [x] Debian/glibc checkout fixture now packages the complete current checkout, verifies its digest in-container, and reaches the expected attributable RED without host inheritance. CI compares its exact final phase map/reasons to `tools/fixtures/greenfield-expected-red.tsv`; the fixture remains red while the detector job is green only on an exact match.
-- [ ] Reviews complete. Automated review defects around Bash conditional errexit, explicit exits, P4/P6 persisted action status, dev/offline source resolution, stale locks, checkout coverage, and rollback path safety were remediated. Remaining automated objections are the charter-mandated expected RED/C5 boundary and signed provenance, which the canonical PRD explicitly defers; independent informed review is still required.
+- [ ] Reviews complete. Reviews 80 (`rev-security-02`) and 81 (`rev-974`) requested changes at `3934e03f`; their eight non-overlapping detector findings are being remediated red-first. Current remediation adds canonical-image portability, absolute P3 CLI propagation, exact expected-RED schema/cardinality, passwd-HOME binding, created-path owner/mode policy, real-action P2–P8 fault injection, verified non-empty remote installer execution, and seeded secret-canary/redacted diagnostics. Both old verdicts become void when the remediation head moves and require fresh independent review.
 
 ## Risks / blockers
 
@@ -59,10 +59,25 @@ Implement C1 from the canonical greenfield-install PRD v2: a transactional P0–
 - #869 must remain staged and inactive.
 - Late sequencing input MB-BRAIN-01 is accommodated without implementation or renumbering: P2 covers installer distribution only; P5 owns requested credential capability; P7 leaves an ordered seam for credential-dependent resource provisioning after P5.
 
+## Remediation review controls
+
+- B1 RED: the next-lane harness failed immediately under `ci-base:latest` as root/musl; it now models uid 1001/glibc explicitly and uses Python tree fingerprints instead of GNU `find -printf`.
+- B2 RED: framework/runtime linking consumed bare `mosaic` from PATH after P3 had committed an absolute path. The unified installer now exports/passes `MOSAIC_CLI_PATH`; the linker invokes that absolute artifact, and wizard auto-launch has no stale-PATH fallback.
+- B3 RED: a one-row manifest (`exit=1`) certified any exit-1 log. Full-manifest validation now requires the exact three cases, one exit and P0–P9 row each, pinned require/forbid populations, and rejects malformed/duplicate/unknown rows; shrink is a negative control.
+- B4 RED: uid 1001 with a passwd HOME different from ambient HOME produced P0 PASS. P0 now binds uid, username, passwd HOME and shell and explicitly rejects root and sudo-with-inherited-HOME controls.
+- B5 RED: mode-0777 CLI, mode-0644 identity, and mode-0755 credential storage passed. P3/P4/P5 now apply target owner/group plus executable/shared/private policies; framework credential storage is created 0700.
+- B6 RED: fault injection only wrote `.selftest-*` files. The synthetic path was removed; the P2–P8 matrix enters the normal action flow, proves an action observation occurred, injects after each real phase, and fingerprints rollback.
+- B7 RED: an HTTP-200 empty body exits zero when piped to Bash. The fetched installer must now be non-empty, digest-equal to `tools/install.sh.sha256`, and that exact file is executed; failed/empty/mismatch controls are blocking and CI has a remote immutable-commit arm.
+- B8 RED: raw combined command output was duplicated to terminal and `commands.log`. Both capture layers now redact before output/persistence; a seeded canary is positively emitted by the fake credential-capable registry and must remain absent from terminal, command log, npmrc, generated files and observed argv. The real greenfield fixture also scans those populations.
+- Advisory code review findings are fixed: URL userinfo redaction now handles raw `@`, repeated `:`, percent encoding and multiple URLs in both capture layers; the real greenfield path positively emits its canary through `state_run_captured`; and verified-fetch removes its temporary body after successful execution.
+- Advisory security review's independent trust-root finding is **DEFERRED by canonical PRD v2 §3**, which explicitly excludes signed provenance. README now states precisely that the same-origin sidecar detects empty/corrupt/inconsistent publication but cannot authenticate against repository/server compromise; no stronger claim remains.
+- The web1 no-manifest representativeness observation is recorded but intentionally not acted on: it is explicitly outside these eight blockers. This remediation does not weaken or otherwise change P9's manifest-presence assertion.
+
 ## Verification log
 
 - `bash -n` and ShellCheck pass for all changed shell surfaces; `git diff --check` passes.
-- `bash tools/install-state-machine.test.sh` passes, including exact P0–P8 rows, good/bad discrimination, persisted P4/P6 action failures, P2–P8 rollback, unsafe/overlapping/symlink roots, stale `active.json`, and fatal journal initialization.
-- `bash tools/install-next-lane.test.sh` passes, including exact `@next` versions, immutable source fallback, source-build/archive-failure rollback, offline `--dev`, explicit refs, and prerelease suffix mismatch.
+- `bash tools/install-state-machine.test.sh` passes, including exact P0–P8 rows, passwd-HOME/privilege discrimination, owner/group/mode attacks, persisted P4/P6 action failures, no synthetic fault implementation, unsafe/overlapping/symlink roots, and fatal journal initialization.
+- `bash tools/install-next-lane.test.sh` passes inside `ci-base:latest`, including exact `@next` versions, immutable source fallback, source-build/archive-failure rollback, offline `--dev`, explicit refs, prerelease suffix mismatch, absolute P3 CLI propagation, secret redaction, real-action P2–P8 rollback, and stale projection recovery.
+- Comparator controls pass for verdict drift, unexpected exit, manifest shrink, missing phases, duplicate rows, unknown cases, and unknown kinds. Verified-fetch controls pass for successful execution and failed/empty/digest-mismatch rejection.
 - `bash tools/e2e-install-test.sh --lane next --source checkout --git present` returns the required expected RED in clean Debian/glibc as uid 1001: installer P0/P1/P2/P3/P7 PASS; P4/P5/P6/P8 and P9 blocking; no `Done.` claim; checkout archive digest pinned and current framework installer exercised. `tools/verify-greenfield-expected-red.sh` converts that expected detector result into a green CI assertion and fails on any unreviewed verdict drift.
-- Earlier repository gates passed: `pnpm typecheck`, `pnpm lint`, `pnpm format:check`, `pnpm test:installer`, upgrade manifest/rollback/durable-snapshot/migration suites, and focused `@mosaicstack/mosaic` tests with an isolated npm prefix. Full rerun is required after final edits.
+- Earlier repository gates passed: `pnpm typecheck`, `pnpm lint`, `pnpm format:check`, upgrade manifest/rollback/durable-snapshot/migration suites, and focused `@mosaicstack/mosaic` tests with an isolated npm prefix. Full exact-remediation rerun is required before push.