docs: update collections overview table with current artifact counts

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## Component

Documentation

## Bug Description

`docs/getting-started/collections.md` contains a hand-maintained artifact count table that is now stale after PR #1245 added the `owasp-docker` skill to the `security` and `hve-core-all` collections. The table shows incorrect counts across the `security` and `hve-core-all` rows, and the total artifact count in the introductory text is wrong.

**Current docs vs. actual YAML counts:**

| Collection | Doc: Agents | Doc: Prompts | Doc: Instructions | Doc: Skills | Actual: Agents | Actual: Prompts | Actual: Instructions | Actual: Skills |
|---|---|---|---|---|---|---|---|---|
| `security` | 9 | 14 | 19 | 5 | 9 | 15 | 18 | 10 |
| `hve-core-all` | 51 | 63 | 102 | 12 | 51 | 64 | 101 | 17 |

The introductory text says "221 artifacts" but the `hve-core-all.collection.yml` manifest now contains **233 artifacts**.

## Expected Behavior

The table rows for `security` and `hve-core-all` and the "221 artifacts" introductory text should reflect the current counts sourced from `collections/security.collection.yml` and `collections/hve-core-all.collection.yml`.

## Steps to Reproduce

PR #1245 (`feat(skill): introduce owasp-docker`) added:
- `.github/skills/security/owasp-docker/SKILL.md` (new skill)
- Updated `collections/security.collection.yml` and `collections/hve-core-all.collection.yml` with the new skill entry

`docs/getting-started/collections.md` was not updated in that push.

## Additional Context

- **Stale file:** `docs/getting-started/collections.md` — the `security` and `hve-core-all` rows in the collections table and the "221 artifacts" intro text
- **Source of truth:** `collections/security.collection.yml`, `collections/hve-core-all.collection.yml`
- **Triggering commit:** PR #1245 (feat(skill): introduce `owasp-docker`)
- **Related enhancement:** Issue #1317 proposes auto-generating this page from YAML manifests to prevent future drift; this issue tracks the immediate factual correction needed in the interim.

> [!NOTE]
>
> 🔒 Integrity filter blocked 1 item
>
> The following item were blocked because they don't meet the GitHub integrity level.
>
> - [#435](https://github.com/microsoft/hve-core/issues/435) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
>
> To allow these resources, lower `min-integrity` in your GitHub frontmatter:
>
> ```yaml
> tools:
> github:
> min-integrity: approved # merged | approved | unapproved | none
> ```
>
>

> Generated by [Documentation Update Check](https://github.com/microsoft/hve-core/actions/runs/24691891936/agentic_workflow) · ● 3.6M · [◷](https://github.com/search?q=repo%3Amicrosoft%2Fhve-core+is%3Aissue+%22gh-aw-workflow-call-id%3A+microsoft%2Fhve-core%2Fdoc-update-check%22&type=issues)

Open docs/getting-started/collections.md and compare the security and hve-core-all rows with collections/security.collection.yml and collections/hve-core-all.collection.yml. Update the two table rows and introductory total to match the manifests, then verify the documented counts against those YAML source files.

Written by the indexing model from the issue text.