Tasks: roll running sessions onto a refreshed environment

Phase 4 of 4. Derived mechanically from design.md and testing-plan.md. A DAG: tasks at the same indent are independent.

[x] 1. the_loop/envstate.py — declared, fingerprint, process_environ, compare. No value reaches a log line or a return value in clear except through the mapping declared returns. Requirements: R1.1, R1.7, R2.1, R2.3, R5.2Test: T1
- [x] 1a. tests/test_envstate.py — the pure comparisons, the fresh re-read, the real /proc read, and the None paths. Test: T1
[x] 2. TmuxRunner.respawn_in — respawn-pane -k -t … -c … -e … -- <resume argv>. Requirements: R1.4 Test: T2
[x] 3. TmuxRunner(env_provider=…) — fold the provider's names into spawn_in's -e list behind _supports_env; the-loop's own three names last; default None leaves today's argv untouched. Requirements: R4.1, R4.2, R4.3, R5.1 Test: T2
- [x] 3a. Wire the provider at the two real construction sites (the dispatcher and the standing-session runner) so a spawn re-reads the file. Requirements: R4.1
- [x] 3b. tests/test_tmux_runner.py — argv assertions for 2, 3 and 3a. Test: T2
[x] 4. core.sessions.environment_drift — the read half: per session, its live pids, what they hold, and the names that differ. Requirements: R3.1, R3.4Test: T4
[x] 5. core.sessions.restart_sessions — selection, liveness, resumability, respawn, probe, verification, rows and exit code. Requirements: R1.1–R1.7, R2.1–R2.4 Test: T3
[x] 6. sessions restart subcommand — --all, <work-item>, --dry-run, --format json; renders core's rows. Requirements: R1.1, R1.2, R1.3, R2.4Test: T3, T5
[x] 7. status reports drift — sessionEnvironment in lifecycle.status_all, one line in each of the two renderers, ok untouched. Requirements: R3.1–R3.5Test: T4
[x] 8. Tests — tests/test_sessions_restart_integration.py covering T3, T4 and the redaction assertions of T6. Test: T3, T4, T6
[x] 9. Docs — docs/cli/commands/sessions.md (the subcommand, and the argv exposure stated plainly), docs/cli/commands/status.md (the new line), docs/capabilities/interactive-sessions.md (the capability). Test: T5
[x] 10. Evidence — verification (including the real-tmux transcript, T7), security review, self-review, documentation. Test: T7, T8