feat(cli-hub): bump to 0.4.0 and add CLI-Matrix analytics

The cli-matrix command family (#355) shipped to the repo but never reached
PyPI: version stayed at 0.3.0, which was already published, so the publish
workflow skipped it. Bump to 0.4.0 in both setup.py and __init__.py to trigger
a fresh release carrying matrix.py / matrix_skill.py.

Also instrument the matrix surface under the existing unified PostHog
mechanism (flat event names, breakdown by properties — same convention as
cli-install / cli-launch):

- matrix-install:   install / dry_run / skill_only / error, with scope +
                    installed/skipped/failed counts (headline conversion signal)
- matrix-preflight: capability-coverage check with covered/capabilities/gaps
- matrix-discover:  list / search / can / recipes, with query + result count
- matrix-info:      info / doctor inspects of a single matrix

All events honor CLI_HUB_NO_ANALYTICS and the provider switch. 163 tests pass.