agents: drop the count and the coverage claim (FRE-359 verdict B)

FRE-359's verdict is B: the page's thirteen is the registry's first thirteen
of eighteen rows, so the count, "every coding agent The Nook supports" and
"Supported agents" all overstate or understate the app. The permitted
sentences are the CTO's, verbatim.

- agents.tsx: head description, ogTitle and H1 paragraph replaced with the
  verdict's sentences; title/H1 "Supported agents" -> "Agent coverage".
- agents.test.ts: the stale NOOK-336 guard asserted "all thirteen" and
  the 13-name roster, so it passed in lockstep with the page. It now asserts
  no count of any form, no completeness phrase, and that the rows are a
  subset of the 18-name registry list (copied 2026-10-29, @ f4258034) in
  registry order. The table still lists 13 rows; regenerating it from the
  registry is its own ticket, and the guard no longer pretends otherwise.
- FeatureBreakdowns.tsx / IslandExtras.tsx: the landing "13 agents:" bullet
  and the "13 agents" marquee chip lose the count; the chip becomes
  "Agents wired in".

bun test src/routes/nook/agents.test.ts: 4 pass. Server security and appcast
suites fail in this checkout on missing env (Environment validation failed /
mainDBConnection), unrelated to these files.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

src/routes/nook/agents.tsx

@@ -1,5 +1,7 @@
 /**
- * `/agents` on the Nook subdomain — supported agents and their event coverage.
+ * `/agents` on the Nook subdomain — the agent roster and each row's event
+ * coverage. It states no agent count and claims no completeness over the
+ * registry (FRE-359 verdict B).
  *
  * The registry below mirrors `AgentSpec.all` in the app
  * (~/Code/the-nook/Sources/NookCore/Agents/AgentSpec.swift) and each agent's
@@ -282,19 +284,19 @@ export default function NookAgentsPage() {
     <>
       <EdgeCacheHeaders maxAge={300} />
       <PageHead
-        title="Supported agents"
-        description="Every coding agent The Nook supports — all thirteen, with each hook's exact event coverage and what you can do from a card: watch sessions live, answer permission prompts, unblock work."
-        ogTitle="The 13 agents The Nook supports, and what each hook sees"
+        title="Agent coverage"
+        description="The coding agents The Nook connects to, with the events each hook reports and what you can do from a card: watch sessions live, answer permission prompts, unblock work."
+        ogTitle="The coding agents The Nook connects to, and what each hook sees"
       />
       <SubdomainHeader />
       <main class="min-h-screen px-[8vw] py-[8vh]">
         <h1 class="text-text mb-3 text-3xl font-bold tracking-tight sm:text-4xl">
-          Supported agents
+          Agent coverage
         </h1>
         <p class="text-subtext0 mb-2 max-w-2xl text-lg">
-          The Nook watches thirteen coding agents in one place — your menu bar and
-          notch show every session that is running, thinking, or blocked, and a
-          card answers permission prompts without leaving your keyboard.
+          The Nook watches coding agents in one place — your menu bar and notch
+          show sessions that are running, thinking, or blocked, and a card can
+          answer a permission prompt without leaving your keyboard.
         </p>
         <p class="text-subtext1 mb-10 max-w-2xl text-sm">
           Each agent reports its own set of events. "Allow / Deny from a card"