docs: reconcile SPEC with turn-span, install modes, self-upgrade, and the journal

[tsilenzio]

Summary

Dedicated spec-update session folding four changes of accumulated drift back into SPEC.md, per the ADRs' SPEC-impact lists:

• Turn-span activity (ADR-0013): the staleness/commit-timeout model is replaced throughout with the turn-span test, a new "Awaiting-input & the safety cap" section, Notification as the seventh hook event with notification_type in the line schema, the supervisor-loop pseudocode rewritten, and STANDARD_TIMEOUT/COMMIT_TIMEOUT/GC_THRESHOLD replaced by SAFETY_CAP/AWAITING_INPUT_GRACE in the constants list.
• Install modes and self-upgrade (ADR-0014): a new install/uninstall CLI section (three install modes, atomic-rename replacement, the .disabled stand-down), and the self-upgrade and disable-flag exits added to "Self-exit & crash recovery" and the loop.
• Decision journal (TODO-003): journal behavior under daemon, the decision line and staleness verdict under status, JOURNAL_* constants, and journal.rs in the module list.
• This week's fixes: the 1 KiB command bound in the schema and Atomicity sections (replacing the PIPE_BUF rationale), hold_since counting battery time only, and the battery-cap-as-veto invariant.
• Housekeeping: module list gains install.rs/journal.rs, the bash-hook migration section is marked completed (2026-07-11), the unit-test and scenario lists match the current suite, and ADR-0013/0014 SPEC-impact sections are marked applied.

Test plan

• Cross-checked each section against the shipped code on main (94a458f): constants match config.rs, the loop pseudocode matches daemon::run, the awaiting-input type set matches event.rs
• Swept for stale terms (STANDARD_TIMEOUT, COMMIT_TIMEOUT, GC_THRESHOLD, staleness-as-release, six-hook references): none remain
• CI (docs-only change; conventions checks)