## Summary

Implements the sort logic for `winget list` output, completing the
feature requested in #4238. Builds on PR #6177 (settings parsing + CLI
handling).

### Changes

**Sort orchestration** (`WorkflowBase.cpp`):
- `SortInstalledPackagesTableLines` — resolves sort fields from CLI
`--sort` > settings `output.sortOrder` > query-aware default, determines
direction, sorts via `std::stable_sort`, applies permutation back.
- When the free-text query (`-q`) is used and no sort preference is
configured, relevance ordering is preserved. If `output.sortOrder` is
configured, it is respected even with queries.
- `FAIL_FAST_MSG` for unrecognized sort field values — ensures invalid
enum values crash loudly in debug builds.

**Sort helper** (`PackageTableSortHelper.h/.cpp`):
- `SortablePackageEntry` — holds pre-computed case-folded sortable
fields, computed only for fields needed via `ComputeSortFieldMask`
bitmask optimization.
- `CompareByField` — case-insensitive ordinal comparison using
pre-computed `FoldCase` values.
- `SortBy` — template sort executor used by the workflow; standalone
`SortEntries` wrapper available for unit tests.
- `SortField` enum uses flag-bit values (`uint32_t`) with
`DEFINE_ENUM_FLAG_OPERATORS` for efficient bitmask field tracking.

**CLI integration** (`ListCommand.cpp`):
- `--sort` (repeatable, limit 6), `--ascending`/`--asc`,
`--descending`/`--desc` arguments.

**Argument validation** (`Command.cpp`):
- Validates `--sort` values in `ValidateArguments`, following the
`--scope`/`--authentication-mode` pattern.

**Documentation** (`list.md`):
- `--sort`, `--ascending`, `--descending` in options table. New "Sorting
output" section.

### ⚠️ Behavior change: default sort order

Previously, `winget list` output preserved the source's natural ordering
(source-determined relevance ranking). **This PR changes the default to
sort alphabetically by name (ascending)** when no `--sort` argument, no
`-q` query, and no `output.sortOrder` setting is configured.

| Scenario | Behavior |
|----------|----------|
| No query, no settings, no `--sort` | Sorts by name (ascending) — **new
default** |
| `-q` query with no sort preference | Preserves source relevance
ordering (unchanged) |
| `--sort relevance` or `"sortOrder": ["relevance"]` | Preserves source
ordering explicitly |
| `"sortOrder": []` (empty array) | Same as no setting — applies default
name sort |
| `output.sortOrder` configured + `-q` query | Settings override
relevance (explicit user preference wins) |

**To restore previous (source-determined) ordering:**
- CLI: `winget list --sort relevance`
- Settings: `{ "output": { "sortOrder": ["relevance"] } }`

> **Note:** An empty `sortOrder` array is equivalent to the setting not
being present — it does not disable sorting. Use `"relevance"`
explicitly to preserve source ordering.

### Design decisions

| Decision | Rationale |
|----------|-----------|
| **Default sort by name** | When no settings and no query, sort
alphabetically by name — most natural default for browsing installed
packages. |
| **Relevance preservation with queries** | Free-text query (`-q`)
without configured sort preserves source relevance ranking. Settings
override this if configured — explicit user preference takes priority. |
| **`stable_sort`** | Preserves relative order for multi-field sorting
(e.g., `--sort source --sort name` groups by source, alphabetical
within). |
| **Flag-bit `SortField` enum** | Enables `ComputeSortFieldMask` to skip
unused field extraction — measurable win for large package lists. |
| **Pre-computed `FoldCase`** | Expensive case-folding done once per
entry at construction, not on every comparison call. |
| **`FAIL_FAST_MSG` on invalid sort** | Catches enum drift at
development time rather than silent misbehavior. |

### How validated

**Unit tests** — 20 test cases:
- 18 sort tests in `PackageTableSortHelper.cpp`: single/multi-field
sorting, both directions, edge cases, case-insensitive comparison,
relevance no-op
- 1 drift detection test in `Command.cpp`: reads
`ListCommand::GetArguments()` limit and validates against known
`ConvertToSortField` strings — breaks if enum changes without updating
limit
- 1 enforcement test in `Command.cpp`: verifies `SetCountLimit(6)`
rejects 7 `--sort` values with `TooManyArgError`

**Manual testing** — 21 scenarios on `wingetdev` (Debug x64): defaults,
single/multi-field sorts, direction flags, query + sort interaction,
settings precedence, edge cases, invalid input. All passing.

Fixes #4238

---------

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>