fix(app): preserve selected Den organization

[benjaminshafii]

Summary

• Make ensureDenActiveOrganization() prefer the locally selected Den org before falling back to the server session's active org.
• Prevent background org sync from writing the previous server active org back over the user's current Settings org selection.

Evidence

Build verification

• pnpm install -- passed in the fresh worktree.
• pnpm --filter @openwork/app build -- passed.

API verification

• No API contract changes.

UI verification

• Not run via Chrome MCP in this turn. This patch targets the org-selection state path that can make cloud sections look unscoped when switching organizations.

Test instructions

1. Sign in to OpenWork Cloud with access to at least two orgs.
2. Open Settings -> Cloud.
3. Switch the active organization.
4. Verify cloud sections, including Marketplaces & Plugins, refresh for the selected org and do not snap back to the previous org's data.

[vercel]

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Project	Deployment	Actions	Updated (UTC)
openwork-app	Building	Preview, Comment	May 9, 2026 3:20am
openwork-den	Building	Preview, Comment	May 9, 2026 3:20am
openwork-den-worker-proxy	Building	Preview, Comment	May 9, 2026 3:20am
openwork-landing	Building	Preview, Comment, Open in v0	May 9, 2026 3:20am
openwork-share	Building	Preview, Comment	May 9, 2026 3:20am