Task: Implement the Icon Theme Locator feature

TASK-DESCRIPTION

Create: sources/desktop/icon_theme_locator.h
Create: sources/desktop/icon_theme_locator.cpp
Create: tests/icon_theme_locator_test.cpp
Create: tests/12-icon-theme-locator.sh The locator resolves an icon name through the icon theme search path, and implements the requirements in prompts/features/07-icon-theme-locator.md. The test builds its own XDG tree under a temporary directory, so it reads no real theme.

TASK-OUTPUT

Produce these complete files in this order, then the VERIFICATION: line: 1. sources/desktop/icon_theme_locator.h 2. sources/desktop/icon_theme_locator.cpp 3. tests/icon_theme_locator_test.cpp 4. tests/12-icon-theme-locator.sh

TASK-CONTEXT

The icon search rules are described in documents/12-desktop-loading-and-provenance.md section 3. A lookup returns every candidate with its theme, size, and context rather than a single winner.

TASK-FILES

Operation	Path
create	`sources/desktop/icon_theme_locator.h`
create	`sources/desktop/icon_theme_locator.cpp`
create	`tests/icon_theme_locator_test.cpp`
create	`tests/12-icon-theme-locator.sh`

TASK-VERIFY

Run: make test from the repository root.
Expected: exit status 0, and tests/12-icon-theme-locator.sh reports ok.

TASK-FEATURES

prompts/features/07-icon-theme-locator.md

TASK-ACCEPTANCE

ICON-THEME-LOCATOR-R001
ICON-THEME-LOCATOR-R004
ICON-THEME-LOCATOR-R005
ICON-THEME-LOCATOR-R006
ICON-THEME-LOCATOR-R007
ICON-THEME-LOCATOR-R009
ICON-THEME-LOCATOR-R012

OUTPUT: the four complete files in the order listed, ending with the VERIFICATION: line.