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-agent/src/events.rs

@@ -385,7 +385,7 @@ impl Bus {
             }
         };
         let (tx, _) = broadcast::channel(CHANNEL_CAPACITY);
-        // Priority: HIVE_DEFAULT_MODEL (from hyperhive.model in agent.nix) >
+        // Priority: HIVE_DEFAULT_MODEL (from services.hyperhive.agent.model in agent.nix) >
         // persisted runtime override > compiled-in DEFAULT_MODEL.
         // The nix config always wins on rebuild; the persisted file is kept
         // for within-session tracking only (see persist_model / set_model).