[MM-16] Add bounded working-state projection and resume contract

[bug-superman]

MM-16: Add bounded working-state projection and resume contract

Parent

#771

Checkpoint

MC-4A Session continuity

What to build

Track current goal, open threads, decisions, immediate next steps, and corrections in a bounded rebuildable working-state projection.

Acceptance criteria

• Only fixed sections are stored.
• Working state excludes durable profile, complete worklogs, and large tool bodies.
• The initial budget is enforced.
• Close/reopen and resume/fork rules are deterministic.
• The same source is not duplicated in memory segments.

Required tests

• Section schema
• budget
• close/reopen
• restart/resume/fork
• dedupe with durable memory

Benchmark

20-case continuity subset; working-state continuity >=95%.

Blocked by

• [MM-15] Add rebuildable per-session context manifest #794 (MM-15)

Rollout and rollback

Discard and rebuild working state; session transcript remains authoritative.

[Astro-Han]

Superseded by #1615 (automatic long-term memory lifecycle, SQLite-based; accepted by maintainers 2026-07-30, PR ① #1770 merged). This MM-16 work item never landed outside draft PR #820 and is replaced by the #1615 design and its LongMemEval/MSC evaluation plan.