Refresh base-demo AI context for current representative environment

[codeforester]

Context

.ai-context/manifest.md still says the representative environment direction will add service, infrastructure, UI, and environment-modeling commands. That is stale: base-demo now includes services, environments, Compose infrastructure, a React/Vite console, and multi-language fixtures.

The AI context should match the current README, manifest, contract registry, and representative-environment docs so basectl export-context base-demo gives assistants accurate repo state.

Scope

• Update .ai-context/manifest.md so it describes the current committed representative environment, not future work that already landed.
• Mention the services and environments commands as current manifest-declared commands.
• Mention the service catalog, Compose infrastructure, multi-language service fixtures, React/Vite console, build targets, and BASE_DEMO_SERVICES_DRY_RUN=1 dry-run startup contract where appropriate.
• Preserve the concise AI-context style; do not duplicate the full README.
• Add validation guard coverage in tests/validate.sh if needed so this stale wording does not return.

Validation

• ./tests/validate.sh
• git diff --check
• Optional: basectl export-context base-demo --format markdown --print includes the refreshed wording.

Dependencies

None. This can be implemented before Base v1.6.0.