docs: describe the document vault in the README highlights

The roadmap parenthetical becomes a shipped feature bullet.

README.md

@@ -36,7 +36,8 @@ Try the [live demo](https://demo.healthlog.dev) to see a working install — sig
 
 - **Every vital on one timeline.** Weight, blood pressure, pulse, glucose, body composition, sleep, SpO₂, respiratory rate, mood, and cycle tracking — charted with trends, moving averages, and clinical reference ranges (ESH 2023, ADA 2024), overridable with the targets your clinician set.
 - **Clinical signals, opt-in and additive.** Validated self-checks for mental wellbeing and sleep (WHO-5, PHQ-9, GAD-7, Sleep Condition Indicator — official questionnaire wording, calm crisis-resource handling), grip strength, a 0–10 pain score, waist and body measurements, and a longevity lab panel — each added through one signal registry, so a new signal wires into charts, correlations, the coach, the FHIR map, and the API at once.
-- **Records, structured.** Allergies and family history as encrypted structured records that flow into the doctor report, plus lab values you key in or scan from a printed report — OCR extracts the stated values, units, and dates for you to review and confirm before anything is saved. HealthLog transcribes what a report says; it never interprets or diagnoses from it. (A general document vault is on the roadmap; immunization records are deliberately out of scope.)
+- **Records, structured.** Allergies and family history as encrypted structured records that flow into the doctor report, plus lab values you key in or scan from a printed report — OCR extracts the stated values, units, and dates for you to review and confirm before anything is saved. HealthLog transcribes what a report says; it never interprets or diagnoses from it. (Immunization records are deliberately out of scope.)
+- **A document vault for the paper trail.** An opt-in module stores every letter, report, and scan encrypted at rest — PDFs and photos preview inline, Office and text files stay download-only, and nothing user-uploaded can ever execute in the app. One searchable timeline with type, condition, and year filters, drag-and-drop and paste-to-upload, bulk filing, undo-able delete with a 30-day grace, and per-file/per-account limits the operator tunes.
 - **Context that explains the numbers.** An opt-in environmental module folds weather, daylight, and temperature in as influence signals (winter darkness against mood, heat against blood pressure) using a home location you set, so a pattern has somewhere to point.
 - **Your devices, one server.** Withings, WHOOP, Oura and Polar sync over OAuth2, Google Health connects Fitbit and Pixel Watch through your own Google Cloud client, Nightscout streams CGM glucose, an Apple Health `export.zip` folds your full history in, and the native iOS app streams HealthKit live. A per-metric source priority decides which reading is canonical when wearables overlap.
 - **Medication tracking that tells the truth.** Flexible schedules (weekly injections, weekday-only, intervals, PRN, cyclic), a configurable intake window per dose, and a traceable dose history where every slot reads taken, late, skipped, or missed — the same ledger the compliance rate is computed from, so the percentage can never disagree with the timeline.