Fix: show the splash image on Ghostty over SSH

[kinncj]

Symptom

heimdall-dashboard shows the ASCII splash instead of the inline logo when run over
SSH from Ghostty (e.g. Mac Ghostty → Linux workstation). Locally on macOS Ghostty the
image renders fine — same terminal, different result.

Root cause

Image detection delegates to rasterm.IsKittyCapable() (v1.1.2), which recognises
Ghostty only via TERM_PROGRAM == "ghostty". SSH and tmux do not forward
TERM_PROGRAM (rasterm's own comment notes this), while TERM=xterm-ghostty — set by
Ghostty's terminfo — is forwarded. So over SSH the check fails and we fall back to
ASCII, even though the controlling terminal can render Kitty graphics.

Fix

splash.go now treats TERM=xterm-ghostty as Kitty-graphics-capable in addition to
rasterm's checks. One helper, used where IsKittyCapable() was called directly. The
existing TERM_PROGRAM=ghostty (local macOS) path is unchanged.

Tests

• TestKittyCapableDetectsGhosttyByTERM — TERM=xterm-ghostty with no TERM_PROGRAM/
  KITTY_WINDOW_ID (the SSH case) is capable; case/whitespace tolerant; a plain
  xterm-256color is not.
• TestKittyCapableKeepsTermProgramPath — the local macOS path still works.
• Full suite green (305 tests).

[Copilot]

Pull request overview

This PR fixes terminal image-capability detection so heimdall-dashboard can render the inline splash logo when run over SSH from Ghostty (where TERM_PROGRAM is not forwarded), instead of falling back to ASCII.

Changes:

• Add a kittyCapable() helper that treats TERM=xterm-ghostty as Kitty-graphics-capable, falling back to rasterm.IsKittyCapable() otherwise.
• Switch the splash renderer’s Kitty branch to use kittyCapable() instead of calling rasterm.IsKittyCapable() directly.
• Add unit tests covering Ghostty-over-SSH detection and ensuring the existing TERM_PROGRAM=ghostty path still works.
• Document the fix in the changelog.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
CHANGELOG.md	Notes the Ghostty-over-SSH splash image fix and explains the detection change.
app/internal/tui/splash/splash.go	Introduces kittyCapable() and uses it to select Kitty image rendering when TERM=xterm-ghostty.
app/internal/tui/splash/splash_test.go	Adds tests for the SSH TERM-based Ghostty detection and the existing TERM_PROGRAM path.