feat: adopt the 2026-08-13 T3 upstream batch

[rynfar]

Adopts the 2026-08-13 T3 Code upstream review batch, everything the developer approved except the pull request surfaces work, which lands separately in its own PR to keep this one reviewable.

What's here

Twenty-two upstream commits, replayed in upstream order, plus one Pylon adaptation commit. The headline fixes:

• Tooltips render above dropdowns (#6241). Pylon's popover, menu, select, combobox and autocomplete positioners all sit at z-[130] while the tooltip sat at z-70, so tooltips rendered behind every dropdown. Now z-[140].
• Invalid HTML entities no longer crash mobile markdown (#6495). String.fromCodePoint threw a RangeError on out-of-range numeric entities and took the whole markdown block down.
• Changing themes preserves appearance mode (#6343). Switching theme could re-infer a fresh System preference and flip a dark UI to light.
• Source control settings work on relay environments (#6230) — a remote-mode defect.
• The typed prompt survives a draft changing repo (#6393) — previously lost.

The rest: cmd/ctrl+click on pull request links and sidebar PR numbers opens the host in the browser (#6278 → #6378, a dependent pair), Connect environment deregistration from any client (#4844 → #6442), command palette subtitles with project favicons (#6330), Codex collaboration prompt tuning (#6432), the Android sidebar settings cog (#6520), mobile blockquotes across wrapped lines (#6482), and a handful of layout and hover fixes (#6322, #6385, #6414, #6423, #6451, #6509).

Pylon adaptations

One commit at the end covers the fork-specific work:

• Rebranded the T3 Code / T3 Connect copy that arrived with #4844 and #6378 to Pylon / Pylon Connect. The T3Connect* filenames and the t3-connect route slug stay as compatibility identifiers, matching the existing T3ConnectSidebarSignIn.tsx. app.t3.codes is left alone — it is the inherited hosted origin, not branding.
• #4844's only conflict was in MobileClientsUserProfilePage.tsx, where Pylon had already rebranded copy that upstream restructured. Resolved Pylon-first: upstream's ClerkUserProfilePage shell and typography, Pylon's product copy.
• Collapsed #6330's THREAD_COMMAND_SUBTITLE_VARIANT knob. It shipped as a "flip this while reviewing" switch with three variants, but nothing outside the file ever passed one, so two of the three were dead.
• Dropped a no-op class expression in #6509's aspect-ratio toggle, where a ternary branch tested a condition its own branch had already decided.

Note that #4844 is inert until Pylon owns a Clerk application, same as O9 and O11 in the ledger. It is taken for drift reduction.

Verification

• vp test run over all 11 touched test files: 301 passed.
• Typecheck on @t3tools/web, t3, @t3tools/mobile, @t3tools/client-runtime, @t3tools/contracts: clean. The only diagnostics are pre-existing suggestion-level Effect hints in files this branch does not touch.
• vp lint over all 47 changed source files: clean.

One trap worth recording: the first test run exited 0 while 5 tests were failing. The mobile markdown tests resolve @t3tools/mobile-markdown-text through a pnpm store copy made at install time, and I had installed before cherry-picking, so they ran against pre-cherry-pick source. Re-installing relinked it and all 301 pass.

Not verified in a real client — happy to do a browser pass on request.

Model: Claude Opus 5. Harness: Claude Code.

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[github-actions]

Thread transfer impact

⚠️ The latest CI run did not produce a thread transfer result for 4e38560.

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