fix(desktop): avoid duplicate sidebar tabs

[beastpu]

Summary

• add an opt-in AppLink mode that lets desktop tab shells open or activate an existing tab on primary clicks
• use that mode for sidebar navigation links so clicking an active destination does not also trigger default anchor navigation
• cover the foreground tab activation path and web fallback path with AppLink tests

Fixes #4284

Tests

• pnpm --filter @multica/views exec vitest run navigation/app-link.test.tsx
• pnpm --filter @multica/views typecheck
• git diff --check

[vercel]

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[truffle-dev]

Routing the primary nav through openInNewTab(href, undefined, { activate: true }) so it dedupes via openTab is the right shape.

One scoping question: the pinned sidebar items still render a plain AppLink (SortablePinItem, app-sidebar.tsx:203) and go through push, which navigates the active tab's router rather than open-or-activating by path. So clicking a pinned issue/project after switching to a different tab reproduces the same duplicate. #4284 lists "issue, or project," and pins are a primary way to open those — is leaving them on the old behavior intentional, or should they get activateTabOnClick too?

[YOMXXX]

Verified the review scope: pinned issue/project rows both go through SortablePinItem, and that component was still rendering AppLink without activateTabOnClick, so pinned sidebar clicks could still route through push instead of desktop open-or-activate.

I applied the minimal fix locally:

• SortablePinItem now renders <AppLink ... activateTabOnClick />, covering both pinned issues and pinned projects.
• app-sidebar.test.tsx now renders the mocked SidebarMenuButton.render element and asserts loaded pinned links carry the activation flag.

Validation:

• pnpm --filter @multica/views exec vitest run layout/app-sidebar.test.tsx navigation/app-link.test.tsx ✅ 12 tests
• pnpm --filter @multica/views typecheck ✅
• pnpm --filter @multica/views lint ✅ exits 0, existing warnings only
• git diff --check ✅

I attempted to push the amended commit to beastpu:codex/fix-4284-duplicate-tab, but GitHub returned 403 Permission to beastpu/multica.git denied to YOMXXX despite maintainerCanModify=true.

Patch branch with the exact amended commit is available here: YOMXXX:codex/fix-4284-pinned-tabs (431dff67d).

[truffle-dev]

Confirmed — I diffed YOMXXX:codex/fix-4284-pinned-tabs against this PR's head, and it closes exactly the gap I flagged with nothing extra. The only production change is the one-liner at SortablePinItem (app-sidebar.tsx:203):

-render={<AppLink href={href} draggable={false} />}
+render={<AppLink href={href} draggable={false} activateTabOnClick />}

so pinned issues and projects now take the same openInNewTab(href, undefined, { activate: true }) path as the rest of the nav (629/693/717) instead of falling through to push. The app-sidebar.test.tsx change is a genuine regression guard, not just coverage: the old mock silently dropped SidebarMenuButton's render element, so the pinned link was never asserted at all; it now renders that element and checks the activation flag is present.

On the 403: that's expected rather than a config problem — maintainerCanModify=true grants push to this head branch to base-repo maintainers, not to another fork's contributor, so YOMXXX can't push to beastpu's branch. The clean landing paths are either a multica-ai maintainer pulling the amended commit straight onto the branch:

git fetch https://github.com/YOMXXX/multica.git codex/fix-4284-pinned-tabs
git push https://github.com/beastpu/multica.git FETCH_HEAD:codex/fix-4284-duplicate-tab

or, since the delta is a single prod line, @beastpu just applying it directly here. Either way the scope is right and the behavior is pinned.

[YOMXXX]

Opened standalone PR #4353 with the complete duplicate-tab fix including the pinned-sidebar gap: #4353

This is the same patch branch truffle-dev confirmed above, packaged as a direct PR because I cannot push to beastpu:codex/fix-4284-duplicate-tab from my fork.