test(drive): track transcript padding gauntlets

[kitlangton]

Why

The transcript-padding gauntlets existed only as untracked local files, while their network-chaos branch had drifted 20 commits behind main. The branch also retained an unmerged annotated-recording hardening change needed for trustworthy capture dimensions and clip validation.

What Changes

• Track two current-V2 padding probes:
  • the seeded network state machine sampled throughout reconnect faults
  • a controlled-shell workload with streamed progress and connection kills
• Share one transcript-padding detector and write distinct frame/text evidence for each finding.
• Document both commands and their evidence directory.
• Preserve the existing recording hardening while reconciling it with newer keypress and pointer overlays:
  • reject negative clip holds
  • use shared header dimensions
  • reject unsupported filesystem birthtimes for mark alignment

Scope

The probes remain opt-in manual diagnostics. They do not run in normal CI or alter OpenCode behavior.

Verification

cd packages/drive
bun run drive check test/manual/tui-regressions/padding-gauntlet.ts
bun run drive check test/manual/tui-regressions/padding-tools.ts
bun run check
bun run test

• 274 Effect tests and 61 CLI integration tests pass.
• Live current-V2 smoke runs sampled 172 frames across both workloads with zero padding findings.