fix(admin): edit button silently fails for items in All Content tab

[bokelley]

Closes #2692

Admin users clicking "Edit" on blog posts in the All Content tab got no response — the button appeared to do nothing across all browsers.

Root cause: editContent(id) searched only myContent (the user's own posts). Items displayed in the All Content tab come from adminContent (a separate array populated by GET /api/admin/content). When the ID wasn't in myContent, the function returned early silently.

Fix: Three changes in editContent:

1. Fall back to adminContent with String(c.id) === String(id) (matching the type-safe comparison already used in openDetailModal)
2. When item comes from adminContent, async-fetch the full record from /api/admin/content/:id before opening the modal — the admin list endpoint omits content and tags, which would otherwise render the body editor blank and overwrite the article body on save
3. Resolve committee slug from item.committee_slug (flat field on admin list items) as fallback to item.collection?.committee_slug (nested shape on myContent items)

Non-breaking justification: Client-side JS fix for a broken UI path; no API, schema, or protocol changes.

Pre-PR review:

• code-reviewer: approved — all three blockers (missing content field, collection field shape mismatch, ID type coercion) addressed; save path via PUT /api/me/content/:id confirmed admin-permissive at server level
• internal-tools-strategist: approved — async fetch pattern mirrors openDetailModal; editFromDetailModal path unaffected; no new duplicate pathways

Triage-managed PR. This bot does not currently iterate on review comments or PR conversation threads (only on the source issue). To unblock:

• Push fixup commits directly: gh pr checkout <num> → fix → push.
• Or re-trigger: comment /triage execute on the source issue.

See #3121 for context.

Session: https://claude.ai/code/${CLAUDE_CODE_REMOTE_SESSION_ID}

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