test(g3): prove WAL-only recovery

[Freshair129]

Summary

• Fail the G3 recovery fixture on materialized-file removal errors other than NotFound and verify listed files are absent before reopen.
• Capture the final stable frontier in both temporal and relational fixtures and require recovered state to cover it.
• Add a regression for non-NotFound removal errors; no production code changed.
• Record the CI Clippy follow-up and prevention in the G3 RCA.

Local verification

• G3 oracle + crash simulation: 20 passed (3 G3, 17 crash).
• Bitemporal + relational U2 + transaction U3: 15 passed.
• Python reference suite: 1 passed.
• cargo clippy --no-default-features --all-targets -- -D warnings: passed.
• cargo clippy --all-targets -- -D warnings: passed.
• cargo fmt --all -- --check: passed.
• npm run docs:validate: 0 violations in 241 files.
• git diff --check: passed.

This is bounded local G3 test evidence only; it does not assert broad HQL2/P7/P8/P13, hosted cross-platform qualification, release, or deployment readiness.