feat(scripts): check-cli-command-ids also requires every module under src/commands to BE a command

The oclif command table is a glob over the emitted tree
(`"commands": { "strategy": "pattern", "target": "./dist/commands", "glob": "**/*.js" }`),
so every module under `packages/cli/src/commands/` is taken to be a command. A helper
placed beside the command it serves has no default-exported command class, and oclif
then writes a `findCommand ... not found` warning to stderr on EVERY `os` invocation,
whatever the user ran — which corrupts `os validate --json` for any consumer that reads
both streams.

`check-cli-command-ids.mjs` already walks that directory and already derives an id per
file; it asked the opposite question (does a command-id literal outside the CLI resolve
to a derivable path), and a module with no command class still yields a derivable path.
So the second duty lands in the same walk: no new traversal, no new verification surface.

- The predicate follows the INHERITANCE CHAIN, across files. `build.ts` extends `Compile`
  and `migrate/index.ts` extends `MigratePlan`; a predicate accepting only
  `extends Command` would false-red both, which is how a guard gets switched off.
- It PARSES (via `scripts/ts-parse.mjs`) rather than matching text: `create.ts`,
  `generate.ts` and `init.ts` are scaffolders whose template literals spell
  `export default ...` hundreds of lines before the module's own real class.
- It reads SOURCE, never `dist`, so it needs no build and inherits no stale artefact.
- The module population is the EMITTED set, deliberately wider than the id population: a
  dotted or non-kebab base cannot be a command id but `tsc` still emits it and the glob
  still loads it, and those are the shapes a misplaced helper takes.
- Exemptions are declarative and SELF-RETIRING — an entry reds once its file leaves the
  population or starts exporting a command class.
- Zero examined modules is a refusal, not a pass.

Duty one is unchanged: the derived id and topic sets are set-equal to the previous
implementation (74 ids, 12 topics).

Claude-Session: https://claude.ai/code/session_01TSf4DV7ziu4V5j73e46b7c
Co-authored-by: Claude <noreply@anthropic.com>

Author: claude