fix(ghosts): keep superseded ghosts of the live turn until it ends

[Juliusolsson05]

Fixes #730

What was wrong

gcSupersededGhosts evicted a superseded ghost 5 s after supersedure, even while its turn was still semantic.currentTurn (for example, a tool still running). ghostsFromSemanticTurn re-mints any missing block of the current turn on every tick, so the same uuid came back without supersededBy. Its committed entry had already been reconciled, so nothing superseded it again. 30 s later it orphaned with an updatedAt newer than the JSONL tail, which is the state the render predicate still paints: a duplicate of the committed block.

Evidence (counted, not reasoned)

I scanned all 1,955 ghost logs in ~/Library/Application Support/agent-code/ghost-logs for a uuid written superseded and then written again un-superseded:

• 3,231 re-mints in 419 logs. By provider: 2,128 Codex (resp_…) and 1,103 Claude (msg_…).
• By block type: 3,010 tool_use, 137 text, 84 thinking.
• 3,226 were orphaned afterwards.
• Supersede→re-mint gap: minimum 5,040 ms, which is the 5 s grace plus the 1 s sweep. p50 was 10.2 s.

The fixture testing/fixtures/ghost-remint/ is one real Claude Bash tool_use ghost, unedited: superseded at +2.9 s, re-minted with a fresh createdAt at +8.9 s, orphaned at +38.9 s.

Fix

gcSupersededGhosts takes currentTurnId and spares that turn's ghosts. This is the same exemption gcHiddenOrphanGhosts got in #725, and the sweep in useIpcSubscriptions.ts passes the same id to both. Retention is bounded to one turn's blocks.

Tests

ghosts.remint.test.ts drives the real functions with the fixture: mint, reconcile against the committed entry, sweep at the recorded re-mint time, then the next semantic tick.

• Fail-first: on main, the re-minted ghost has no supersededBy.
• Mutation: dropping the exemption turns the test red.
• The ghost is still evicted once the turn changes, or when no turn is current.
• Renderer suite: 3,035 of 3,036 pass. The one failure is recentCommandHistory under Node 25 (localStorage.clear); it passes on Node 24, so it is environmental and unrelated.
• tsc -b is clean.

Not verified

• The live app (house rule).
• The sweep wiring in useIpcSubscriptions.ts has no test; the replay harness omits the timer by design (see reconstructSlices.ts).

🤖 Generated with Claude Code

Review disposition (A Codex, B Pi; 2 rounds)

Finding	Disposition
A/B: the sweep call site was untested (passing null survived every test)	Fixed (3d95d941): sweepGhosts composes the three reducers and reads currentTurn itself; the composed tick is tested
B2: the supersede guard in ghostsFromSemanticTurn was unpinned	Fixed: late-delta identity test
B round 2: swapping the TTL and GC timings inside sweepGhosts survived	Fixed (89c0e51d): orphan-TTL test through the composed tick
A MAJOR: after a reload, a semantic replay re-mints a ghost whose superseded marker the log reduction dropped	A different, pre-existing route; filed as #1233 with the reviewer's repro
B3: >= versus > at the eviction boundary	Unobservable at a 1 s sweep; no change

Round 2: A and B both MERGE-READY. Recount of the on-disk evidence by B: 419 logs (exact), minimum gap 5,040 ms (exact).