docs(ptt): land Baseline Candidate v0.9.3 — capability-based desktop PTT

Applies the gen2 desktop-PTT review summary
(`gen2/chanora-desktop-ptt-review-summary-v0.9.2.md`) to our doc set
with the owner rulings PTT-OPEN-001 through PTT-OPEN-006 resolved as
accepted decisions DEC-023 through DEC-028:

  * DEC-023 Windows Global PTT P0 / MVP
  * DEC-024 macOS Global PTT P0 / MVP with permission UX
  * DEC-025 Linux officially-tested env: GNOME on Wayland only
  * DEC-026 Mouse side buttons supported (Win + macOS; Linux portal)
  * DEC-027 PTT diagnostics: capability + availability only, no
            raw key codes ever
  * DEC-028 Missed-key-up watchdog: P0

Requirements (SysRS / SRS) and architecture (SysDes / SAD / SDD)
gain the desktop-PTT ID set the gen2 summary describes:

  SysRS-296..302  -> SysDes-142..148
                  -> SRS-195..203
                  -> SAD-071..079
                  -> SDD-081..092

ID totals advance from 295 / 141 / 194 / 70 / 80 to 302 / 148 / 203
/ 79 / 92. The strict layered sourcing rule (`SRS -> SysDes` only,
`SAD -> SRS` only, `SDD -> SAD` only) is preserved; the
`tools/validate_docs.py` validator reports zero undefined refs and
zero direct-layer-rule violations.

New document:

  * `docs/architecture/desktop-ptt-architecture.md` — capability
    ladder (L0Focused, L1GlobalShortcut, L2GlobalHoldToTalk,
    L3GlobalWithMouseButtons, L4DeviceAware reserved), Windows /
    macOS / Linux strategies, privacy rule, audio-gate rule,
    missed-key-up watchdog, release-readiness evidence requirement,
    traceability summary.

Doc addenda (Baseline Candidate 0.9.3):

  * `privacy/privacy-policy.md` — no raw key history, capability-
    dependent Global PTT, UI reflects actual runtime capability
  * `security/threat-model.md` — THREAT-PTT-001..006
  * `security/diagnostic-redaction-audit-report.md` —
    REDACT-PTT-001..006 banned field list enforced by `PttSanitizer`
  * `release/platform-release-policy.md` — per-platform evidence
    fields, no over-claim on untested Linux compositors
  * `release/release-readiness-go-nogo-record.md` — RR-PTT-001..008
    release-readiness items
  * `verification/swe4-unit-verification-plan.md` —
    SWE4-UV-035..039
  * `verification/swe5-software-integration-verification-plan.md` —
    SWE5-IV-015
  * `verification/swe6-software-verification-plan.md` — SWE6-SV-017
  * `verification/sys4-system-integration-verification-plan.md` —
    SYS4-SIV-016
  * `governance/traceability-matrix.md` — full PTT trace rows +
    verification map
  * `governance/decision-impact-assessment.md` — DEC-023..028
    impact matrix
  * `governance/product-decision-register.md` v0.9.9 entry
    recording DEC-023..028 in the decision table and the status
    table at §7
  * `governance/document-index.md` — adds
    `desktop-ptt-architecture.md` to the controlled set
  * `architecture/proof-of-concept-plan.md` —
    PoC-PTT-001..005 platform items
  * `references/external-references.md` — Windows Raw Input,
    macOS event-tap, Linux GlobalShortcuts portal references
  * Both validation reports
    (`baseline-candidate-validation-report.md`,
    `repo-format-validation-report.md`) bumped to v0.9.3 with the
    new ID totals (302 / 148 / 203 / 79 / 92).

README §"Desktop Push-to-Talk" added between Architecture Overview
and Repository Layout: capability levels, per-platform strategy,
privacy posture, missed-key-up watchdog.

Tooling:

  * `tools/validate_docs.py` copied from the gen2 zip into the
    repo tree (was previously available only inside the zip).
    Reports zero undefined refs, zero direct-layer-rule violations,
    English-only CJK check passes. The 35 "old package-style
    filename" hits are pre-existing and identical to the gen2
    baseline (they live in `path-migration-map.md` and config-ID
    headers of governance docs and are intentional per the path
    migration policy).
  * `.gitignore` adds `/gen2/` so the externally-provided review
    package does not enter the repo.

No code changes in this commit; B (the implementation split into
`transmit_active` / `capture_active`, `PttCapabilityLevel`
reporting, `PttSanitizer` diagnostics rule, and the UI capability
badge) follows in a separate commit.

docs/privacy/privacy-policy.md

@@ -106,3 +106,17 @@ TBD.
 | Version | Date | Description |
 |---|---|---|
 | 0.9.2 | 2026-05-14 | Corrected Apple App Store Connect upload gate to 2026-04-28 and checked full-package naming, references, and coverage. |
+
+
+## Desktop Push-to-Talk Privacy Addendum (Baseline Candidate 0.9.3)
+
+Per SysRS-302 / SRS-202 / DEC-027, the Chanora desktop PTT subsystem operates under the following privacy rule:
+
+- Chanora shall not log, persist, or transmit raw keyboard key codes, scan codes, virtual-key values, keysyms, or key-press timing sequences.
+- The user-initiated diagnostic export shall include only the detected PTT capability level (`L0Focused`, `L1GlobalShortcut`, `L2GlobalHoldToTalk`, `L3GlobalWithMouseButtons`, or the reserved `L4DeviceAware`), the active backend identifier (a fixed string per implementation, for example `"raw-input"`, `"event-tap"`, `"gnome-wayland-portal"`, `"focused"`), and the bound input class (`"keyboard"`, `"mouse-side-button"`).
+- The bound key value itself is never included in any diagnostic, even when the user invokes the export explicitly.
+- Whether Global PTT is available depends on the operating system, the user-granted permission set, the display server, and the available input backend. Where Global PTT cannot be honoured, Chanora falls back to Focused PTT and reports the fallback honestly through the UI capability badge.
+
+| Version | Date | Description |
+|---|---|---|
+| 0.9.3 | 2026-05-15 | Added desktop Push-to-Talk privacy addendum: raw key history is not recorded or exported; Global PTT is capability-dependent and the UI reflects actual runtime capability. |