fix(ui): streamline mobile Show Page navigation

[cyhhao]

Summary

• Preserve literal /show/:sessionId/ document navigation when an installed mobile PWA opens an Agent-provided Show Page link.
• Give the mobile Show Page app the full viewport with no AppShell side padding, brand header, or bottom navigation.
• Replace the old framed app header with the compact chat-style back/title/annotation bar.

Evidence

• Unit/component: 42 focused Vitest cases passed, including PWA routing, AppShell chrome, and the mobile Show Page header.
• Static/build: UI lint baseline and production build passed.
• Scenario: local Incus worktree regression at 390x844 confirmed a 390px-wide shell and iframe, 49px header, two controls, and no duplicate brand or bottom chrome.
• Residual manual check: physical iOS installed-PWA link interception remains for the integration acceptance pass.

Scenario IDs: none (no matching catalog entry).

Dependencies: none.

Known-by-design ledger: none.

[cyhhao]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: 7a790007b4

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[cyhhao]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. You're on a roll.

Reviewed commit: 7429357571

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".