feat(run): Add smart short ID resolution for templates and playlist items

[proboscis]

Summary

• Add smart resolution to runbox run <short_id> that can resolve any executable reference (template or playlist item) by short ID
• Display clear resolution info before execution showing what was matched
• Provide clear error messages for ambiguous matches with all candidates listed

Changes Made

Storage Layer (runbox-core/src/storage.rs)

• Added ResolvedTarget enum with Template and PlaylistItem variants
• Added ResolveTargetError enum for resolution failures (NotFound, Ambiguous, Storage)
• Added Storage::resolve_target() method implementing smart resolution:
  1. Templates: exact match on template_id
  2. Templates: prefix match on normalized ID
  3. Playlist items: prefix match on hex short ID
• Added 4 unit tests for resolve_target functionality

CLI (runbox-cli/src/main.rs)

• Updated runbox run command to accept optional [TARGET] positional argument
• Added cmd_run_smart() function that:
  • Resolves the target to template or playlist item
  • Displays resolution info (what matched, template, command)
  • Delegates to template execution
• Updated help text with examples for smart resolution

Examples

# Smart resolution by template prefix
$ runbox run echo
Resolved: template "Echo Message" (tpl_echo)
  Template: Echo Message (tpl_echo)
  Command:  ["echo", "Hello, {name}!"]

# Smart resolution by playlist item short ID
$ runbox run a1b2c3d4
Resolved: playlist "daily" (daily) item 0 "Echo Hello" (tpl_echo)
  Template: Echo Message (tpl_echo)
  Command:  ["echo", "Hello, {name}!"]

# Ambiguous short ID
$ runbox run test
Error: Ambiguous short ID "test" matches 2 items:
  [template]       test_sec  "Test Second" (tpl_test_second)
  [template]       test_ech  "Test Echo" (tpl_test_echo)

Use more characters or specify explicitly:
  runbox run --template <id>
  runbox playlist run <playlist> <item>

# Explicit template (bypasses smart resolution)
$ runbox run --template tpl_echo

Acceptance Criteria

• runbox run <short_id> resolves templates by prefix
• runbox run <short_id> resolves playlist items by hex short ID
• Ambiguous matches produce clear error with all candidates
• Resolution info displayed before execution (what matched, template, command)
• --template flag still works as explicit override
• -- <command> direct execution still works
• Dry run shows resolution + what would execute

Testing

• All 55 unit tests pass
• All CLI integration tests pass
• Manual testing confirms resolution works correctly

Closes: ISSUE-033