CMRT 30: Library table CMRT track name column

[Swarnadip-Kar]

Introduces a CMRT track name column to the main library table,
showing the canonical track’s “Artist – Title” for any track in a
multi-member CMRT group, along with a color swatch and tooltip.
cmrt_groups/cmrt_members already exist from Phase 1 and are
populated by the grouping pipeline (CMRT 24‑28).

Changes

trackschema.h

• Add three virtual column name constants (cmrt_track_name,
  cmrt_is_canonical, cmrt_offset) produced by the library_view
  self‑join, following the pattern of LIBRARYTABLE_COVERART.

columncache.h / columncache.cpp

• Add one visible ColumnCache entry (COLUMN_LIBRARYTABLE_CMRT) and
  two internal‑only entries (CANONICAL, OFFSET) with no display
  name and width 0. The visible column uses kDefaultColumnWidth*3
  to accommodate the “Artist – Title” text alongside the swatch.

librarytablemodel.cpp

• Extend library_view with LEFT JOINs on cmrt_members, cmrt_groups,
  and a self‑join on library AS cmrt_canonical.
• Emit cmrt_track_name (canonical track’s “Artist – Title”),
  cmrt_is_canonical (cg.canonical_track_id = library.id), and a
  gated cmrt_offset (NULL unless group_id is present).
• Qualify the formerly bare mixxx_deleted reference as
  library.mixxx_deleted to avoid ambiguity with the self‑join.
• Qualify coverart_digest as library.coverart_digest for the
  same reason.
• Mark cmrt_is_canonical and cmrt_offset as internal columns
  (isColumnInternal).
• Hide the CMRT column by default (isColumnHiddenByDefault) since
  most libraries have few multi‑member CMRT groups.

basetracktablemodel.h

• Document the three new virtual columns in the rawValue() comment
  (same style as the existing COVERART entry).

basetracktablemodel.cpp

• Wire Qt::DecorationRole (QVariantMap with isCanonical flag) and
  Qt::ToolTipRole (canonical status or offset text) for the CMRT
  column, reading sibling values via rawSiblingValue().
• Return the plain “Artist – Title” text for kDataExportRole.
• Register CmrtDelegate in delegateForColumn().
• Hide the column by default in isColumnHiddenByDefault().

trackmodel.h / basesqltablemodel.cpp

• Add SortColumnId::CmrtGroup (appended before IdMax, respecting
  the append‑only contract for controller‑script compat).
• Map it to COLUMN_LIBRARYTABLE_CMRT in initSortColumnMapping().

cmrtdelegate.h / cmrtdelegate.cpp (new)

• CmrtDelegate draws a 4px swatch (green = canonical, orange =
  member) followed by elided canonical‑track text.
• Falls back to “--” when library_view returns NULL (no group or
  lone‑member group).
• Reuses the hotcue “Green” (0x32BE44) for consistency; member
  color is a distinct orange, not an error red.

CMakeLists.txt

• Register cmrtdelegate.cpp alongside keydelegate.cpp.

Notes for reviewers

• Swatch colours deliberately reuse the existing hotcue “Green”
  (0x32BE44) rather than introducing a new green, for visual
  consistency with cue colours elsewhere in Mixxx.
• Beat‑grid/cue transfer between CMRT members (the “Use CMRT grid &
  cues for CMRT members” preference) is explicitly out of scope
  here—it requires its own design pass.

Depends on: cmrt-fixup-threshold-reanalyze-timestamp (#39)

[coveralls]

Coverage Report for CI Build 28698862293

Coverage decreased (-0.04%) to 30.251%

Details

• Coverage decreased (-0.04%) from the base build.
• Patch coverage: 220 uncovered changes across 5 files (21 of 241 lines covered, 8.71%).
• 3 coverage regressions across 2 files.

Uncovered Changes

File	Changed	Covered	%
src/library/basetracktablemodel.cpp	100	0	0.0%
src/preferences/dialog/dlgpreffingerprint.cpp	77	0	0.0%
src/library/tabledelegates/cmrtdelegate.cpp	28	0	0.0%
src/library/librarytablemodel.cpp	30	18	60.0%
src/library/tabledelegates/cmrtdelegate.h	3	0	0.0%
Total (7 files)	241	21	8.71%

Coverage Regressions

3 previously-covered lines in 2 files lost coverage.

File	Lines Losing Coverage	Coverage
src/preferences/dialog/dlgpreffingerprint.cpp	2	0.0%
src/library/basetracktablemodel.cpp	1	9.0%

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Coverage Stats

Relevant Lines:	117029
Covered Lines:	35402
Line Coverage:	30.25%
Coverage Strength:	117724.01 hits per line

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💛 - Coveralls