Task: Implement the Desktop Entry Locator feature

TASK-DESCRIPTION

Create: sources/desktop/desktop_entry_locator.h
Create: sources/desktop/desktop_entry_locator.cpp
Create: tests/20-desktop-entry-locator.sh
Create: tests/50-desktop-search-path-live.sh The locator builds the XDG application and autostart search paths, resolves a desktop file identifier, and implements the requirements in prompts/features/05-desktop-entry-locator.md. The portable test builds its own XDG tree under a temporary directory; the live-state test compares the model with this host and declares its prerequisites.

TASK-OUTPUT

Produce these complete files in this order, then the VERIFICATION: line: 1. sources/desktop/desktop_entry_locator.h 2. sources/desktop/desktop_entry_locator.cpp 3. tests/20-desktop-entry-locator.sh 4. tests/50-desktop-search-path-live.sh

TASK-CONTEXT

Search-path facts and the observed host values are in documents/09-desktop-file-search-paths.md. The locator reads XDG_DATA_HOME, XDG_DATA_DIRS, XDG_CONFIG_HOME, XDG_CONFIG_DIRS, and HOME, and never writes.

TASK-FILES

Operation	Path
create	`sources/desktop/desktop_entry_locator.h`
create	`sources/desktop/desktop_entry_locator.cpp`
create	`tests/20-desktop-entry-locator.sh`
create	`tests/50-desktop-search-path-live.sh`

TASK-VERIFY

Run: make test from the repository root.
Expected: exit status 0, with tests/50-desktop-search-path-live.sh reporting PASS or WARN and never FAIL.

TASK-FEATURES

prompts/features/05-desktop-entry-locator.md

TASK-ACCEPTANCE

DESKTOP-ENTRY-LOCATOR-R001
DESKTOP-ENTRY-LOCATOR-R004
DESKTOP-ENTRY-LOCATOR-R006
DESKTOP-ENTRY-LOCATOR-R014
DESKTOP-ENTRY-LOCATOR-R017
DESKTOP-ENTRY-LOCATOR-R018
DESKTOP-ENTRY-LOCATOR-R021

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