switch off the browser relay, pending extraction into a plugin

BROWSER_RELAY_PORT is gone and the second listener no longer starts. The Chrome
extension, api/browser/ and the /browser screen all stay on disk — this is going
to be extracted, and deleting it means writing it again.

Three things had to move together, and the middle one would have failed the boot
on its own:

  server.tsx    the listener, commented out with the variable name recorded
  hono.ts       the /api/browser mount, closed
  registry.ts   the 'browser' capability's claim on /browser, dropped

assertCapabilityTotality checks both directions: check 2 refuses to start on a
capability claiming a prefix nothing serves. Unmounting the router alone would
have left the registry describing it, and the server would not have come up.

The capability itself survives because it also claims /scrape, which shares
nothing with the relay — it launches its own headless chromium through playwright
and never speaks to the extension.

The comment in server.tsx carries the two facts that are not recoverable by
reading the remaining code. First, the port is an INPUT TO A CREDENTIAL:
relay-auth.ts derives each extension's token as HMAC(JWT_SECRET,
'officer-browser-relay-v1:${port}:${userId}:${salt}'), so bringing the relay back
on a different number silently invalidates every paired browser — reported by the
extension as "Relay not reachable", which SETUP.md blames on a wrong address,
port or token. Second, it cannot come back as a kernel-assigned port:0 like the
other sidecars: the extension is configured by hand and stores the value, so a
port that moves each restart breaks the pairing each restart.

Left alone deliberately: the /browser route in App.tsx, its Dock entry, and the
Settings → Browser Relay panel. They will not work against a closed endpoint.
Removing them is frontend work for the extraction, not part of switching the
listener off.

.env is down to PORT and POSTGRES_URL.

Not typechecked (empty node_modules, frozen installs). Every changed file parses;
the setup section was run and writes two variables.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.env.example

@@ -1,6 +1,5 @@
 # What officer-setup writes. Everything below this block is optional, or is on its way out.
 PORT=9000
-BROWSER_RELAY_PORT=18792
 POSTGRES_URL="postgres://postgres:password@localhost:5432/officer"
 
 # ── Moving to the secret store ─────────────────────────────────────────────────────────────────