Add context command support for chat turns - #1124

Greptile Summary

This PR adds an optional chat.context_command configuration that executes a shell command before each chat turn and appends its stdout to the prompt context, enabling deployments to inject dynamic runtime context without manual copy-paste. The implementation is well-contained across config, a new moltis-common runner module, the chat service, the gateway's external-agent path, and the Codex app-server transport.

• run_context_command in moltis-common handles the hard safety properties correctly: 30-second timeout with kill_on_drop, a 32 KB stdout cap (matching workspace_file_max_chars), and concurrent stderr draining to prevent pipe deadlocks — all addressed concerns raised in prior review rounds.
• Chat turns now call resolve_turn_context which merges project-file context and command output; the sequential ordering is forced by the dependency on working_dir from resolve_project_context.
• External-agent turns (including the Codex app-server) gain a working-dir-aware context resolution and forward command output via ContextSnapshot.project_context; the PR also adds an outer per-turn timeout to CodexAppServerSession::send_prompt and params/delta extraction to extract_message.

Confidence Score: 5/5

Safe to merge — the feature is additive, opt-in (defaults to None), and the command runner correctly handles all known failure modes (timeout, truncation, non-zero exit, pipe deadlock).

The implementation addresses the output-size cap, working-directory propagation, and warn-vs-debug log level that were flagged in prior rounds. No new correctness issues were found across the runner, chat service, gateway, or Codex transport changes.

No files require special attention.

Sequence Diagram

sequenceDiagram
    participant User
    participant ChatService
    participant DB as ProjectService/DB
    participant Cmd as context_command
    participant LLM

    User->>ChatService: chat turn (send)
    ChatService->>DB: resolve_project_context(session, conn)
    DB-->>ChatService: (project_context_str, working_dir)
    ChatService->>Cmd: run_context_command(cmd, working_dir)
    Note over Cmd: 30s timeout, 32KB cap
    Cmd-->>ChatService: command_context (or None)
    ChatService->>ChatService: merge_context_sections()
    ChatService->>LLM: send prompt + merged context
    LLM-->>ChatService: response stream
    ChatService-->>User: streamed response

    Note over ChatService: External-agent path
    User->>ChatService: external agent turn
    ChatService->>DB: resolve_context_working_dir(session)
    DB-->>ChatService: working_dir (or None)
    ChatService->>Cmd: run_context_command(cmd, working_dir)
    Cmd-->>ChatService: context_command_output
    ChatService->>ChatService: context_from_history_with_project_context()
    ChatService->>LLM: "send_prompt(text, ContextSnapshot{project_context})"
    LLM-->>ChatService: ExternalAgentEvents
    ChatService-->>User: streamed response

_{Reviews (3): Last reviewed commit: "fix(context-command): cap output size an..." | Re-trigger Greptile}

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