refactor(daemon): table-ify handleSessionCommands - #1467

Fixes #1458.

Summary

• Replaces the 18-branch if-chain in handleSessionCommands (src/daemon/handlers/session.ts) with SESSION_COMMAND_HANDLER_IMPLS, a handler table keyed by session-routed command name, following the existing snapshot.ts / dispatch.ts pattern.
• Adds DescriptorSessionRouteCommandName to src/core/command-descriptor/registry.ts — the literal union of every command whose daemon.route is 'session', derived from the descriptor registry (mirrors the existing DescriptorDispatchCommandName).
• The table is satisfies Record<DescriptorSessionRouteCommandName, SessionCommandHandler>, so a session-routed descriptor with no matching table entry is a compile error.
• Command-kind groupings are preserved by mapping several command names to the same handler reference (e.g. session_list/devices/capabilities/apps all point at handleSessionInventoryCommandGroup; boot/shutdown/appstate at handleSessionStateCommandGroup; perf/logs/events/network/audio at handleSessionObservabilityCommandGroup; replay/test at handleSessionReplayCommandGroup) — no working handler was split.
• Deletes the fallow-ignore-next-line complexity waiver that gated the old if-chain.
• expectHandlerResponse in request-handler-chain.ts is untouched — it stays as defense-in-depth for raw-wire requests.
• Zero behavior change: every branch's request/response shape, error messages, and ordering are identical; only the dispatch mechanism changed.

Compile-time exhaustiveness demonstration

Per the acceptance criteria, I verified the guard actually fires by temporarily adding a fake session-routed descriptor with no handler entry:

{
  name: 'fake_session_probe',
  catalog: { group: 'internal', key: 'fakeSessionProbe' },
  recordsSessionAction: false,
  daemon: { route: 'session', refFrameEffect: 'preserve' },
  timeoutPolicy: DEFAULT_TIMEOUT_POLICY,
  batchable: false,
},

pnpm typecheck failed as expected:

src/daemon/handlers/session.ts(465,3): error TS2741: Property 'fake_session_probe' is missing in type '{ session_list: SessionCommandHandler; ... }' but required in type 'Record<"apps" | "appstate" | ... | "fake_session_probe" | ... , SessionCommandHandler>'.

The fake descriptor was then reverted before this commit — it isn't part of the diff.

Incidental fix

getSessionCommandKind (src/daemon/daemon-command-registry.ts) had no production consumer left after this refactor (the new table encodes command-kind clustering directly via shared handler references instead of a runtime kind lookup), which tripped the fallow dead-code --production gate. The function and its SessionCommandKind classification are still exercised by daemon-command-registry.test.ts, so I added it to .fallowrc.json's ignoreExports allowlist, following the same pattern already used there for other test-only-consumed exports (e.g. listRegisteredDispatchCommandNames's sibling in dispatch.ts).

Test plan

• pnpm check:tooling (lint, typecheck, layering, depgraph, production-exports, mcp-metadata, build, bundle-owner-files) — green
• pnpm test:unit — 523/523 test files, 4660 tests passing
• pnpm test:smoke — 13/15 passing; the 2 failures (smoke-daemon-clean, smoke-daemon-http) reproduce identically on the unmodified main baseline in this sandbox (real daemon-process spawn is restricted here), unrelated to this change
• Existing handler tests pass unmodified (no test file edits were needed at all — imports of handleSessionCommands are unchanged since its exported signature is identical)

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