refactor(v1): collapse interception to PrimeTunnel and server|elastic

[hallerite]

Stacked on #2503 (which is stacked on #2496).

The interception layer carried a generic plugin system with one used implementation. The tunnel/ package was a discriminated TunnelConfig union, a Tunnel ABC generic over its config, bind_host/bind_port hooks, and a custom bring-your-own-endpoint tunnel. Nothing selects it: no config, doc, skill or test in verifiers sets interception.tunnel, prime-rl and the env repos never touch it, and the default ElasticInterceptionPool hard-pins PrimeTunnelConfig() regardless. StaticInterceptionPool existed for the same bring-your-own case and has no consumer either.

After this PR

• verifiers/v1/interception/tunnel.py is one module: PrimeTunnel (no config, no base class) and TUNNEL_LIMITER. mcp/launch.py keeps importing PrimeTunnel from the same path.
• InterceptionServerConfig has no tunnel field. The server always binds an ephemeral loopback port; when a consumer is remote it exposes that port through a prime tunnel, exactly as the only reachable configuration did before.
• InterceptionConfig is server | elastic. --interception.type static and any interception.tunnel.* flag now fail validation instead of selecting dead code.

Removed: PrimeTunnelConfig, BaseTunnelConfig, Tunnel, CustomTunnel, CustomTunnelConfig, TunnelConfig, make_tunnel, StaticInterceptionPool, StaticInterceptionPoolConfig. None is exported from verifiers.v1 and none is referenced in prime-rl, prime-envs or community-environments. TunnelError is unchanged.

Checks run: ruff check, ruff format --check, ty check verifiers, pytest tests/v1 -m "not e2e" (82 passed), plus a direct check that {"type": "server"} and {"type": "elastic"} validate, static and a tunnel field are rejected, the EnvConfig default is still elastic, and a non-tunnelled server binds loopback.

🤖 Generated with Claude Code

Note

Remove static interception pool and collapse tunnel to PrimeTunnel

• Removes StaticInterceptionPool and StaticInterceptionPoolConfig from the interception config union, factory, and public exports; only server and elastic types remain
• InterceptionServer no longer carries a configurable tunnel field; it constructs a PrimeTunnel directly when requires_tunnel is true, otherwise runs with no tunnel
• InterceptionServer.start always binds an ephemeral port on the server host; remote exposure publishes that port through PrimeTunnel, non-remote returns a loopback URL
• ElasticInterceptionPool._server no longer passes an explicit prime tunnel config to new elastic servers; they use the default server config while retaining pool-level tunnel requirement and state secrets
• Risk: callers that set InterceptionServerConfig.tunnel or instantiate the static interception type will break; the tunnel field and StaticInterceptionPoolConfig discriminator are removed from server.py and pool.py

^{Macroscope summarized 15302bf.}