Add CLI commands to create and delete saved SSH servers

[giraypultar]

Headless installs can now register servers with vibeshell servers add user@host[:port] and remove them with vibeshell servers delete, without opening the desktop UI.

• Optional flags cover the Add Server dialog fields: jump host, agent forwarding, post-login command, group, tags
• Passwords come from SSH_PASSWORD or VIBESHELL_PASSWORD; keys from --identity
• IPC socket extended to handle the new server add/delete operations
• Docs updated (README, cli/README, skills)

[veithly]

Thank you for the focused CLI server-management contribution and its parser/backend tests. This is useful, but I am holding it out of 1.1.0 pending the following correctness and security fixes. The PR now targets dev, our integration branch; please rebase onto current dev.

1. Preserve exact secret bytes. env_nonempty() and the backend add_server_spec() path trim passwords/passphrases. Leading or trailing spaces can be part of a valid secret; validate presence separately and do not normalize the value. Add tests for whitespace-bearing password and key passphrase round trips.
2. Make profile/group/credential changes atomic with the existing metadata/credential transaction model. A credential failure must not leave a partial server, association or sync outbox entry, and delete failures must not remove the secret first. Add injected-failure rollback coverage.
3. Redact the new AddServer/spec IPC variant before Debug logging. The current fallback in redact_for_log clones unmatched messages; the new message carries secret-bearing fields. Add a sentinel-secret regression for password, private key and passphrase and check any activity path as well.

Please retain the noninteractive create/delete UX, explicit deletion confirmation and existing tests while addressing these points. Run strict Clippy, workspace tests and the current release-metadata checks against dev. No merge is being performed until the credential invariants are preserved.

[veithly]

Re-reviewed on 2026-09-29 at e8fd8d0. The head is unchanged since the earlier changes-requested review and now conflicts with dev, so it is still not safe to merge.

The exact-secret-byte, atomic metadata/credential/outbox, and AddServer IPC redaction blockers remain. Two additional compatibility gaps in the current diff should be covered in the revision:

• The GUI add_server adapter discards the existing ServerInput.credential_id when constructing AddServerSpec. Preserve that association rather than silently detaching saved credentials.
• servers delete currently goes directly to deletion without a prompt or explicit noninteractive confirmation flag. Please make that intent explicit. Also reject malformed host:port inputs instead of treating them as literal hosts.

The concrete remediation and acceptance-test plan is in #17, docs/ISSUE_TRIAGE_2026-09.md. Please rebase onto current dev and reuse its transaction/credential paths. This useful feature remains open, not rejected; the existing changes-requested review remains in effect. CI is being moved to manual dispatch, but all required checks are retained.