thv llm: setup and teardown orchestration

[yrobla]

Context

Part of #5016 (RFC: stacklok/toolhive-rfcs#70). Final subtask — depends on all previous subtasks.

Scope

thv llm setup:

• Detects installed AI tools via the tool adapter registry
• Configures each detected tool (Apply)
• Starts the background proxy if any proxy-mode tool is detected
• Triggers the OIDC browser login flow

thv llm teardown:

• Removes gateway configuration from all tool config files (Revert)
• Stops the background proxy
• --purge-tokens flag to also delete cached OIDC tokens from the secrets provider
• thv llm teardown <tool-name> — targets a single tool without affecting others

Acceptance Criteria

• AT: thv llm setup --gateway-url <url> --issuer <issuer> --client-id <id> detects installed tools, configures each, starts the background proxy if any proxy-mode tool is present, and triggers OIDC browser login
• AT: thv llm teardown removes gateway config from all tool config files, stops the proxy, and optionally purges cached tokens with --purge-tokens
• AT: thv llm teardown <tool-name> targets a single tool without affecting others

Dependencies

• thv llm: package skeleton, cobra commands, and config management #5027 (foundation)
• thv llm: OIDC token lifecycle and thv llm token command #5028 (token lifecycle)
• thv llm: localhost reverse proxy for proxy-mode tools #5029 (proxy)
• thv llm: tool adapter registry and per-tool implementations #5030 (tool adapters)

References

• Parent issue: thv llm subcommand for LLM gateway authentication #5016
• RFC: RFC-0070: thv llm subcommand for LLM gateway authentication toolhive-rfcs#70