Function enable 

pub fn enable(
    lua: &Lua,
    cfg: &DebugConfig,
    source_map: Option<Arc<SourceMap>>,
) -> Result<Option<DebugHandle>, DebugError>

Enable the debug backend for lua according to cfg (task 4.1 full wiring).

• When cfg.enabled == false: returns Ok(None). No VM hook is installed, no port is opened, no thread is spawned, and std_debug is NOT exposed to scripts. This is the true zero-cost path (R5.2 / R5.3 / R5.5).
• When cfg.enabled == true: builds a FULLY WIRED backend and returns Ok(Some(DebugHandle)):
  1. a shared [BreakpointSet] (settable while the VM runs),
  2. a [DebugSession] over the VM-thread ends of the command/event channels, installed into the line hook via hook::install (engine-wide jit.off() + a coroutine-crossing EVERY_LINE hook) — this is the VM-thread stop core; inspect/step/continue are processed in its hook loop ON THIS THREAD (the mlua::Lua never crosses a thread, R6 / !Send),
  3. a [Transport] bound to cfg.listen (the OS-assigned port is readable via DebugHandle::local_addr when listen uses port 0),
  4. a shared [DapAdapter] and two bridge threads connecting the transport to the session (see [wiring] for the thread topology).

Thread topology (design “Architecture” / “System Flows”)

One VM host thread (the caller, owns mlua::Lua and the session in the hook) + one socket-bridge thread (sole [Transport] owner: multiplexes inbound socket reads and outbound socket writes, since Transport is !Sync and mpsc has no select) + one event-encoder thread (session events → DAP frames). The socket bridge and encoder share the [DapAdapter] behind an Arc<Mutex<…>> (its seq + correlation table). See [wiring] for the full topology and the inbound-poll / outbound-frame-channel structure.

SHIORI independence (R6)

This function does not import or reference pasta_shiori; any pasta host (or a test harness) drives it directly.

Preconditions

lua must already be constructed on the VM thread.

Source map injection (task 4.2 — pasta-source-map)

source_map is the OPTIONAL immutable shared .pasta↔.lua map (design “Architecture”: Arc<SourceMap> 不変共有). Together with cfg.source_mode (task 4.1) it is threaded to the three .pasta CONSUMERS — the DAP source resolver (task 5.2), the breakpoint translator (task 5.3) and the stepper (task 5.4) — via this injection path: enable → wiring → DebugSession (design 548). The map+mode REACH those points only when BOTH a map is supplied AND cfg.source_mode == SourceMode::Pasta (design 582, requirements 6.1); for None or SourceMode::Lua every consumer keeps its existing default .lua behavior byte-for-byte (requirements 6.2 / 7.2). This task wires the SKELETON only — the consumer LOGIC is tasks 5.x.

Errors

DebugError::Bind if the DAP listener fails to bind; DebugError::Vm if the hook install fails (mlua::Error is stringified at the boundary, it is !Send). The disabled path never errors.