fix: bundle Highlightr SPM resources — stops launch crash (SIGTRAP)

[johnfkoo951]

Problem

Multiple users reported v1.4.6 crashing on launch (EXC_BREAKPOINT / SIGTRAP). The crash report points straight at Highlightr's resource bundle:

0  libswiftCore  _assertionFailure
1  CmdMD         closure #1 in variable initialization expression of static NSBundle.module
5  CmdMD         Highlightr.init(highlightPath:)
6  CmdMD         one-time initialization function for sharedHighlightr
9  CmdMD         SyntaxHighlighter.highlightr(for:)
10 CmdMD         SyntaxHighlighter.highlightCodeBlocks(in:font:theme:)
15 CmdMD         SyntaxHighlighter.applyHighlights(to:font:theme:)
16 CmdMD         MarkdownTextEditor.makeNSView(context:)
...            (during NSPersistentUIRestorer window/session restore)

Root cause — the Swift module wasn't packaged

scripts/package_app.sh copied only the executable into CmdMD.app, never the SwiftPM-generated Highlightr_Highlightr.bundle (highlight.js + the CSS theme files). Highlightr's synthesized Bundle.module accessor traps (it's a fatalError, not a thrown error) when that bundle can't be found — so the first time an editor with a code block renders (which session-restore does automatically), the whole app goes down.

swift run masked it locally because the resource bundle sits right next to the dev binary in .build/.

Fix

• package_app.sh — copy every *.bundle from the release bin dir into Contents/Resources/, so Bundle.module resolves through Bundle.main.resourceURL. (codesign --deep already signs the nested bundle.)
• SyntaxHighlighter — probe for the resource bundle before instantiating Highlightr; if it's somehow still missing, log + disable code highlighting instead of trapping. Defense-in-depth so a packaging slip can never hard-crash the app again.
• test_package_app.sh — assert Highlightr_Highlightr.bundle is present in the packaged app. This regression can no longer ship silently (and the release workflow runs this script).
• Version bump → 1.4.7 (build 13) so users actually receive the fix via the in-app update checker.

Verification

• bash scripts/test_package_app.sh → Bundling resource: Highlightr_Highlightr.bundle + PASS.
• Launched the packaged .app in Split mode on a doc containing a Swift code block: highlights correctly, no crash (this is the exact path that crashed before).
• swift test → 57 passing.

Release

After merge, tag v1.4.7 to trigger the release workflow (it asserts the tag matches CFBundleShortVersionString, now 1.4.7).