Fix marketing site honesty defects after PR #514

[IanFrelinger]

Summary

Fixes remaining user-facing honesty defects in the marketing landing (site/) discovered during post-merge verification of PR #514.

Changes

1. Fixed invented client API in code sample

• Before:site/index.html showed client.SubmitTaskAsync(...) which does not exist on IAshlarClient
• After: Shows AddAshlarClient(baseUrl: "http://localhost:5000") + client.InvokeAsync(HttpMethod.Post, "/api/copilot/task", JsonContent.Create(new { task = "..." }))
• Verified against src/Ashlar.Client/IAshlarClient.cs - real methods are RunAgentAsync, OrchestrateAsync, GetStatusAsync, InvokeAsync, etc.
• Aligns with docs/TesterQuickstart.md which documents POST /api/copilot/task as the task submission route

2. Removed broken Discussions link

• Before: Footer Community section linked to https://github.com/IanFrelinger/Ashlar/discussions (404s)
• After: Removed Discussions link; Issues link remains
• Verified via gh repo view --json hasDiscussionsEnabled → false

3. Fixed OG card filename in site/README.md

• Before: Referenced ashlar-social-card-1280x640.png
• After: References ashlar-og-flat-1200x630.png (the actual file used in index.html)
• Both files exist in assets/brand/, but only ashlar-og-flat-1200x630.png is used in the live meta tags

4. Repository homepage metadata (requires manual action)

• Current state:gh repo view --json homepageUrl shows "https://github.com/IanFrelinger/Nexo"
• Attempted:gh repo edit --homepage returned HTTP 403: Resource not accessible by integration
• Required action: Manual update in GitHub repository settings → Homepage to either:
  • https://github.com/IanFrelinger/Ashlar (self-referential), or
  • Leave blank until GitHub Pages is configured

Testing

Verification performed

• ✅ Read src/Ashlar.Client/IAshlarClient.cs to confirm SubmitTaskAsync and ExecuteTaskAsync do not exist
• ✅ Read docs/TesterQuickstart.md to verify correct API usage (POST /api/copilot/task with InvokeAsync)
• ✅ Ran gh repo view IanFrelinger/Ashlar --json hasDiscussionsEnabled,homepageUrl to confirm discussions disabled and homepage pointing to Nexo
• ✅ Verified assets/brand/ashlar-og-flat-1200x630.png exists and matches index.html meta tags
• ✅ Reviewed diff to confirm no unintended changes

Testing strategy (blast radius)

• Static HTML/CSS only - no build step or runtime changes
• No kernel/runtime code touched
• Changes limited to site/ directory (marketing content)
• Verified links and code samples against master source of truth

Checklist

• No runtime code changes (static site only)
• Documentation aligned with actual implementation (site/README.md → correct OG card filename)
• No false API claims on landing page
• No broken links to disabled features

Release

• Not a versioned release — skip