hive-c0re: render the new agent option paths into generated agent flakes

meta.rs writes each agent's flake, and it still named the pre-move
`hyperhive.*` paths — so every agent rebuild would print a rename
deprecation warning about a line no human wrote and no operator could fix.
A warning nobody can act on trains everyone to ignore the ones that matter,
which is the whole value of the alias shims.

Repoints the FORWARDED_VAR_OPTIONS table and every other emitted option
assignment (otel.*, docs.source, claudeCodePath, github.enable, user.name,
claudeMemoryMaxBytes) to `services.hyperhive.agent.*`, with the test
expectations that pin the rendered text. The flake input named `hyperhive`
(`hyperhive.url`, `hyperhive.inputs.nixpkgs.follows`,
`hyperhive.nixosConfigurations.*`), hive-tier `services.hyperhive.*` paths,
and the `@hyperhive.local` git identity share the word and are untouched.

Also repoints the same option paths where they appear in comments, rustdoc
and runtime message strings across the other crates — a refusal message
naming `hyperhive.allowedRecipients` sends an operator to a path that will
stop existing. Prose under docs/ is deliberately not in this commit.

Refs #4473

hive-c0re/src/priv_client.rs

@@ -403,7 +403,7 @@ pub async fn write_agent_matrix_token(
 /// (running as root). Writes `<state>/github-token` 0600, chowned to the agent
 /// user so the `gh` wrapper / git credential helper can read it from inside the
 /// container. Single account per agent — no account suffix. The token value is
-/// operator-supplied (for the agent's GitHub integration, `hyperhive.github.enable`).
+/// operator-supplied (for the agent's GitHub integration, `services.hyperhive.agent.github.enable`).
 ///
 /// # Errors
 ///