Default TLS validation on; scope skip-TLS bypass to the configured host

The app shipped with certificate validation bypassed globally and on by
default — InsecureTrustDelegate trusted any cert from any host. That was
the evaluation's P1: anyone on the LAN could MITM call audio, transcripts,
and voiceprints.

The backend's Start9 cert already validates under normal system trust when
the StartOS Root CA is installed in the keychain (confirmed: URLSession
default validation returns 200 against the backend and its fallback), so the
bypass is unnecessary:
- skip-TLS now defaults to off
- when explicitly enabled, the bypass is scoped to the configured host via
  InsecureTrustDelegate.allowsTrustOverride, never "trust any server"
- the host gate is pure and unit-tested (InsecureTrustDelegateTests)

Docs reconciled: AGENTS.md backend/TLS line and Current state.

AGENTS.md

@@ -7,7 +7,7 @@ Native macOS **menu-bar app** that detects video calls, records dual-track audio
 - Project is generated by **XcodeGen** from `project.yml` (`brew install xcodegen`). `*.xcodeproj` is **gitignored** — regenerate, don't edit.
 - Full Xcode lives at `/Applications/Xcode.app`, but `xcode-select` points at CommandLineTools → **set `DEVELOPER_DIR` for every `xcodebuild`**.
 - Bundle id `xyz.ten31.transcripts`; `DEVELOPMENT_TEAM` (Apple Team ID) is set in a **gitignored `Config/Signing.xcconfig`** (copy `Config/Signing.xcconfig.example` and set your team). Keep it stable — a constant signing identity is what preserves TCC grants across rebuilds.
-- Backend: SparkControl gateway at `$SPARK_BACKEND_URL` (a private LAN `.local` host; self-signed cert, so TLS-skip is intentional). Resolution order: a value saved in **Settings → SparkControl backend** (UserDefaults) wins, else the `SPARK_BACKEND_URL` env var, else the placeholder default in `AppSettings.swift`. Diarization = Sortformer/TitaNet (**mono-only**, ~4 speakers/chunk); LLM = Qwen3 via OpenAI-compatible `/v1/chat/completions`; audio via `/api/audio/label-merge`.
+- Backend: SparkControl gateway at `$SPARK_BACKEND_URL` (a private LAN backend — IP or `.local` host; Start9 self-signed cert. Install the StartOS Root CA in the System keychain so normal TLS validation succeeds; skip-TLS is an opt-in, **host-scoped** escape hatch, **off by default** — see `InsecureTrustDelegate`). Resolution order: a value saved in **Settings → SparkControl backend** (UserDefaults) wins, else the `SPARK_BACKEND_URL` env var, else the placeholder default in `AppSettings.swift`. Diarization = Sortformer/TitaNet (**mono-only**, ~4 speakers/chunk); LLM = Qwen3 via OpenAI-compatible `/v1/chat/completions`; audio via `/api/audio/label-merge`.
 
 ## Commands
 First time on a machine — create the local signing config (else `xcodegen generate`/signing won't find a team):
@@ -82,13 +82,14 @@ open /Applications/Ten31Transcripts.app
 - Never commit to `main` or force-push a shared branch; branch first and ask.
 
 ## Current state
-Present tense; overwritten each session. 69 tests pass; `/Applications/Ten31Transcripts.app` matches HEAD and runs; working tree clean and pushed to `origin`/`main`. A full independent evaluation ran 2026-06-13 → `EVALUATION.md` (committed at repo root; overwritten + re-committed each run for a reviewable diff); its findings are triaged into the lists below.
+Present tense; overwritten each session. 73 tests pass; `/Applications/Ten31Transcripts.app` matches HEAD and runs; working tree clean and pushed to `origin`/`main`. A full independent evaluation ran 2026-06-13 → `EVALUATION.md` (committed at repo root; overwritten + re-committed each run for a reviewable diff); its findings are triaged into the lists below. The eval's P1 (TLS) is now **fixed** and verified against the live backend.
 - **Working:** call detection (Meet/Zoom/Teams/Signal), dual-track capture, dual-channel + chunked backend hand-off, speaker reconciliation, recap (`transcript.md` + recap-relay-styled `recap.html`), speaker editor, configurable chunk length, standalone Settings window.
 - **In progress:** the Meet visual fix (reject solid camera-off tiles) is unverified end-to-end — no clean run exists yet; the saved Meet session's `visual_timeline.json` predates the fix.
-- **Work queue (P1 — do first):** the TLS-trust override is global and on by default — it returns `URLCredential(trust:)` for *any* host (`InsecureTrustDelegate.swift:22`; default-on at `AppSettings.swift:109`), so the full mic+system audio, visual timeline, and voiceprint upload is MITM-able by anyone on the LAN. Scope the override to the configured backend host and pin the Start9 root CA (or the leaf SPKI hash); default skip-TLS to off. This gates trusting any later backend-integration test.
+- **Done this session (was eval P1):** TLS validation is now **on by default** and the skip-TLS escape hatch is **scoped to the configured host** (`InsecureTrustDelegate.allowsTrustOverride`, covered by `InsecureTrustDelegateTests`). Supported path = the StartOS Root CA trusted in the System keychain; verified `URLSession` default validation returns 200 against both `192.0.2.1` and the `192.0.2.2` fallback.
+- **Work queue (next up):** wire the backend URL + primary→fallback into config. Today it's a single `backendBaseURL` with no fallback logic, and on this Mac no value is saved (so it resolves to the `your-spark-backend.local` placeholder); the real setup is primary `https://192.0.2.1:62419` → fallback `https://192.0.2.2:62419`.
 - **Known debt (P2 — fix before wider use):**
   - `RecapAnalyzer.mmss()` fatally crashes on NaN/∞ (reproduced 2×); a malformed/MITM'd backend `duration` (e.g. `1e400` → `Double.infinity`) aborts the app at recap-render time — add a finite-guard fallback (`RecapAnalyzer.swift:137`).
-  - README is stale by six phases — still says "Phase 0 (scaffold) / no audio capture, detection, or backend hand-off yet" for a shipped Phase-6 app; same lie in source comment `AppSettings.swift:7`. Rewrite both to match reality.
+  - README is stale by six phases — still says "Phase 0 (scaffold) / no audio capture, detection, or backend hand-off yet" for a shipped Phase-6 app; same lie in source comment `AppSettings.swift:7`; and `README.md:49` still calls skip-TLS "on by default" (now off). Rewrite to match reality.
   - `SessionController` (670 lines, the most concurrency-dense file) has zero unit tests — cover `pendingAutoStop` (auto-start-then-immediate-call-end) and the visual-adoption generation guard before any refactor.
 - **Deferred (P3 — later decision or bulk cleanup; full evidence in `EVALUATION.md`):** `docs/` specs drifted from the dual-channel API + recap phase; `docs/01` §7 lists already-resolved open items; `docs/02` §2.10 claims MenuBarUI features that don't exist; AGENTS.md Layout listings under `Audio/`/`Detection/` are incomplete; the `manifest.json` sha256 contract is specced but never written; env-var precedence footgun (saved URL shadows `SPARK_BACKEND_URL`); `SessionController` owns three jobs (extract the open-panel UI); unused `NSAppleEventsUsageDescription`; unauthenticated LAN backend (consider a shared bearer token).
 - **Known bugs:** Meet speaking-detection is sparse (faint blue border); the mic channel emits some sub-second junk "self" fragments; the same person on desktop-mic vs phone-speakerphone does not unify by voiceprint.