Add Teleport servers that connect through tsh

[giraypultar]

Depends on #10 (this branch contains the CLI server add/delete commit from #10; once #10 merges this PR will show only the Teleport commits).

Saved servers can now be SSH or Teleport. Teleport sessions spawn tsh ssh as the PTY, file/exec operations wrap tsh scp/tsh ssh, and import reads tsh status plus tsh ls.

• CLI add/import and the GUI Add/Edit dialogs accept a required proxy; login/MFA stays with tsh login
• New src-tauri/src/teleport module wrapping tsh for shell, file and exec operations
• Storage schema/sync updated for the new server type; OpenSSH/PuTTY/Tabby importers updated accordingly
• Follow-up commit quotes remote ls paths and passes tsh argument slices by reference so vibeshell-desktop links

[veithly]

Teleport integration is a worthwhile direction. This PR is stacked on #10 and now targets dev, but the current transport implementation changes several safety contracts, so it is not included in 1.1.0 yet. Please resolve #10 first and rebase this work onto the current shared-session architecture.

Blocking items from the current diff:

1. Bound tsh process execution, cancellation and captured output. Synchronous Command.output() has no timeout/output cap, and writing all stdin before draining stdout/stderr can deadlock. Use concurrently drained bounded streams and propagate actual process failure.
2. Preserve file-operation contracts. The cat-based write/create paths must honor overwrite=false with exclusive creation; they must not overwrite an existing destination silently.
3. Preserve binary-read and directory semantics. The binary response needs the expected encoding and real size/truncation fields, not lossy text with binary=true and size=0. The ls fallback trims valid filenames and labels directories as files; either implement a lossless compatible protocol or return an explicit unsupported error.
4. Do not implement directory Sync as unconditional recursive scp while ignoring excluded paths, nested gitignore rules and delete_extra. The returned transfer counts/bytes must reflect actual work rather than fixed success placeholders. Unsupported sync modes should fail clearly until implemented.
5. Drive session connected/disconnected state from verified connection/process lifecycle rather than spawn success or fixed sleeps. Integrate owner-process routing, quick exec/plugin paths and teardown, with tests for authentication failure, EOF and cancellation.

Please add transport-level regression fixtures for overwrite protection, binary data, Unicode/whitespace paths, ignored-file retention and process I/O limits. Existing tests are valuable, but they do not establish these transport guarantees. I am requesting changes rather than merging or closing the contribution.

[veithly]

Re-reviewed on 2026-09-29 at b81e609. There are no new commits since the previous review, the branch still includes #10, and it conflicts with current dev. The earlier process-I/O, lifecycle, binary/file overwrite and sync-contract blockers remain; no merge is being performed.

A smaller first revision focused on authenticated session lifecycle, ownership and explicitly reported transport capabilities would be easier to validate. Use concurrent bounded process I/O with timeout/cancellation, and drive connection state from actual authentication/EOF rather than spawn success or sleeps. File/sync operations may return an explicit unsupported error until they satisfy the normal contracts; lossy text, trimmed ls output and recursive scp are not substitutes for those contracts.

#17 adds a concrete implementation/test plan in docs/ISSUE_TRIAGE_2026-09.md. Resolve #10 first, then cover GUI/daemon ownership, quick/plugin exec, auth failure, EOF, cancellation, binary bytes, whitespace/Unicode paths, overwrite refusal and ignored-file retention. This remains open with changes requested.