feat(cloudflare): add linearvoid-media edge worker for R2 HLS delivery

Replace the ad-hoc `worker.js` with a self-contained `linearvoid-media`
worker under `infrastructure/cloudflare/` that owns `media.linearvoid.tv`.
It serves HLS objects from the R2 bucket, enforcing immutable Cache-Control
on segments, a short TTL on live manifests, plus HLS CORS, OPTIONS
preflight, Range support, and a `/health` probe. Includes wrapper config
with production domain, Vitest unit tests, Miniflare R2 integration tests,
automated deploy workflow, and docs updates.

docs/architecture/README.md

@@ -4,6 +4,20 @@ Linear Void architecture is documented using the [arc42 template](https://arc42.
 
 > Companion docs: see [Documentation README](../README.md) and `adr/` for full decision rationale, alternatives, and consequences.
 
+- [Architecture Documentation for Linear Void](#architecture-documentation-for-linear-void)
+  - [Introduction and Goals](#introduction-and-goals)
+  - [Architecture Constraints](#architecture-constraints)
+  - [Context and Scope](#context-and-scope)
+  - [Solution Strategy](#solution-strategy)
+  - [Building Block View](#building-block-view)
+  - [Runtime View](#runtime-view)
+  - [Deployment View](#deployment-view)
+  - [Cross-cutting Concepts](#cross-cutting-concepts)
+  - [Architecture Decisions](#architecture-decisions)
+  - [Quality Requirements](#quality-requirements)
+  - [Risks and Technical Debts](#risks-and-technical-debts)
+  - [Glossary](#glossary)
+
 ## Introduction and Goals
 
 **Requirements Overview** — Linear Void is an independent **24/7 linear video channel** broadcasting self-owned pre-recorded videos to a primarily US audience via a custom lightweight HTML/CSS/JS SPA with synchronized HLS playback, schedule metadata, public chat rooms, and private 1:1 messaging. Fully independent of third-party video platforms (YouTube, Twitch, etc.).
@@ -386,7 +400,7 @@ _Cache rules baseline_: `.ts`/`.m4s` Cache Everything, long TTL, immutable; `.m3
 
 _Edge security/controls_: enforce HTTPS/WSS + redirect HTTP; WAF baseline; rate limits on abusive patterns (auth/admin); minimize origin exposure.
 
-_Worker & header policy_: Worker logic for immutable cache headers/request normalization where cache rules insufficient (`infrastructure/cloudflare/worker.js`); explicit CORS for HLS.
+_Worker & header policy_: the `linearvoid-media` Worker ([`infrastructure/cloudflare/`](../../infrastructure/cloudflare/), R2-bound) owns `media.linearvoid.tv` and enforces immutable caching for segments, short TTL for live manifests, plus HLS CORS/Range; the `linearvoid-frontend` Worker ([`frontend/wrangler.toml`](../../frontend/wrangler.toml)) serves the static SPA on `linearvoid.tv`. Automated deploys: `workers-deploy.yml` (SPA) and `workers-media-deploy.yml` (media).
 
 _Operations & validation_: verify cache status progression (MISS→HIT), manifest freshness under active playout; track hit ratio, request/error rates, ToS/cost posture.