Extends parse_schwab_email to handle Schwab's RSU Release Confirmation
emails alongside the existing trade confirmations. Adds:
- `VestEvent` dataclass in models.py — carries vest_date, ticker,
shares_vested, shares_sold_to_cover, fmv_at_vest_usd, tax_withheld_usd.
Written to payslip_ingest.rsu_vest_events by a postgres sink (pending
a real email fixture + cross-service DB grant).
- `parse_schwab_email_full()` — new entry point returning both
`list[Activity]` and `VestEvent | None`. The legacy
`parse_schwab_email()` shape is preserved for existing callers.
- Vest-release dispatch heuristic: HTML body mentions "Release
Confirmation" / "Award Vesting" / "RSU Release". On match, extract
vest fields via label regexes; the full vest becomes a BUY Activity
and the sell-to-cover slice becomes a SELL Activity at the same FMV
(net zero cash on the day). Gross vest + sell-to-cover returned so
Wealthfolio gets the full portfolio picture.
- Tests: 3 new (vest roundtrip, unparseable-vest safety, legacy shape
preserved); existing 6 unchanged.
The regex heuristics will need tightening once a real email sample
exists — the HTML structure observed in public Schwab emails may
differ in material ways. For now, unmatched vest bodies return
empty-result (no Activity, no VestEvent) rather than crashing the
IMAP batch.
Part of: code-860