docs(components): deprecate bulk catalog layout

[jcfr]

Onboarding type

• New product onboarding (new components.d/<slug>.yml file)
• Other (catalog change, README fix, infrastructure, etc.)

For new product onboarding — author affirmations

By submitting this PR, I confirm on behalf of my team:

• Skills cleared for open source release per NVIDIA's internal IP review process (six-question check, all answers affirmative)
• License selected: Apache 2.0 / CC-BY 4.0 / Dual (Apache 2.0 + CC-BY 4.0). Specify: _____
• No new license or new third-party component introduced beyond what the source repo already carries
• Source repo is public and under an NVIDIA-owned GitHub org
• .agents/skills/ or skills/ path used for new entries (or existing path retained for legacy entries per components.d/<slug>.yml)

NVIDIA contributors: see the internal onboarding guide for the IP review process details and license selection.

Reviewer checklist (OSS Skills PIC)

• Author confirmations above are checked
• components.d/<slug>.yml entry valid (required fields, unique catalog_dir, path exists in source repo, filename slug matches name)
• SKILL.md frontmatter spec-compliant (at least one sampled)
• No new license or third-party dependency requiring OSRB filing

All PRs

• All commits signed off with DCO (git commit -s).
  If you forgot, run git rebase --signoff origin/main && git push --force-with-lease to retroactively sign all commits in your branch.

Other context (for non-onboarding PRs)

Updates components.d/README.md to promote the flat catalog layout (one entry per skill, one top-level skills/<catalog_dir>/ directory per skill) as the canonical pattern for new components, and marks the bulk layout (single entry's path pointing at a parent directory containing multiple skills) as deprecated.

Concretely:

• path is described as pointing at a single skill directory (one with SKILL.md at its root) rather than a parent of multiple skills.
• The canonical Example section now shows two flat-layout entries instead of the prior single bulk entry.
• A new "Bulk layout (deprecated)" section captures the old pattern inside a GitHub Admonition (> [!IMPORTANT]), explains why the flat layout is preferred (discoverability, explicit naming, decoupling the catalog shape from upstream source structure), and reassures existing components that they keep working — the sync workflow handles both layouts identically.

No changes to the sync workflow, schema validation, or existing components.d/*.yml files — those are unaffected and will be migrated to the flat layout incrementally.