fix(sftp): add breadcrumb go-to-root button beside home icon

[netcatty-bot]

Summary

• Adds a dedicated "go to filesystem root" button (a "/" glyph) next to the existing home icon in the SFTP breadcrumb navigation, per the reporter's follow-up request.
• The home icon keeps its current behavior (jump to the login user's home directory), matching common SFTP-client convention; the new button covers the high-frequency "jump to /" case the reporter described.
• On POSIX panes the button navigates to /; on Windows-style panes it navigates to the current drive root (e.g. C:\) or the UNC share root (e.g. \\server\share).
• The button is disabled when the pane is already at the filesystem root to avoid redundant navigation.

Why

Issue #3211 reports that the breadcrumb home icon navigates to the user's home directory (/root for root) rather than the filesystem root. That home-directory behavior is intentional and consistent with other SFTP clients, but the reporter asked for either a configurable home target or a separate "back to root /" button, since switching between / and absolute paths is a frequent ops workflow. This implements the dedicated root button, which works for every pane without adding a settings surface.

Changes

• application/state/sftp/utils.ts — new pure helper getSftpPathRoot(path, options) deriving the filesystem root (/, drive root, or UNC share root) from the current pane path; returns null when no root can be derived (e.g. relative Windows paths).
• components/sftp/SftpBreadcrumb.tsx — renders the disabled-aware root button in the pinned breadcrumb chrome next to Home, navigating via the existing onNavigate path.
• application/i18n/locales/{en,es,ru,zh-CN,zh-TW}/… — new sftp.goRoot tooltip string ("Go to root" / 回到根目录 / etc.).
• Tests: getSftpPathRoot unit cases (POSIX, drive, UNC, forward-slash-UNC ambiguity) in application/state/sftp/utils.test.ts, and a jsdom interaction test in components/sftp/SftpBreadcrumb.test.ts covering click-to-navigate and the disabled-at-root state.

Testing

• node --test --import tsx components/sftp/SftpBreadcrumb.test.ts application/state/sftp/utils.test.ts components/sftp/SftpPaneToolbar.test.ts — 47 tests pass.
• npx eslint on the changed files — clean.
• npx tsc --noEmit -p tsconfig.json — no errors in touched files (repo has pre-existing unrelated errors elsewhere).
• Manual check suggestion: connect to a host, open SFTP, enter a subdirectory, click the "/" button in the breadcrumb → pane navigates to /; home icon still goes to the home directory.

Fixes #3211

Automation

• Automated implement pass
• Review gate: @codex review (own/bot PRs only)
• Draft until Codex reports clean findings

[binaricat]

@codex review

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Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-08-29T13:26:35.389053Z	3adf86b	Manual request

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Codex Review: Didn't find any major issues. 🚀

Reviewed commit: 3adf86bcd9

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Codex reported no major issues. This PR is marked ready for human review/merge.

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Reviewed commit: 3adf86bcd9

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[chatgpt-codex-connector]

Keep the root action enabled for bare // paths

When a POSIX pane is at the accepted path //, this regex marks it as already at root and disables the new button, even though rootPath is /. The path utilities deliberately preserve double-slash POSIX paths and getParentPath("//") transitions to /, so users in this state cannot use the new control to reach the actual filesystem root. Only disable it when the current POSIX path resolves to the same path as the root target.

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