parse: bump ParserV for the title change; ignore <synthetic> model ids

[yrstm]

Defects (both caught verifying the D round on the devbox)

1. The title fix couldn't reach quiet files. parse: derive row titles from prompts, not instruction files or path drops #15 changed how an existing field is derived without bumping ParserV, so entries scanned by an older binary (fully scanned, junk title, same v:6) were trusted forever. Field case that surfaced it: a stale agentdash -w running since before the upgrade rewrote the cache with old-parser entries every refresh tick, and the new binary accepted every one. ParserV → 7 forces the one-time rescan; the constant's comment now says derivation changes, not just new fields, warrant a bump.
2. <synthetic> in the MODEL column. System-generated claude messages carry model "<synthetic>", which displaced the session's real model (a live row rendered <syntheti…). Now ignored; a session with only synthetic messages reports no model.

Evidence

• TestOldParserVersionEntryIsRescanned replays the stale-watcher case (old-V entry with junk title, unchanged file → rescanned, correct title).
• TestSyntheticModelDoesNotDisplaceReal covers both orders and the synthetic-only case.
• Live: fresh scans by the fixed binary title correctly (verified before this PR); the cache war stops once the old watcher exits and v6 entries age out on first read.
• Local gates green: go test ./... -race, fuzz 15s, vet, golangci 0 issues, parity, bats, darwin build.

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