fix(flet pack): Windows taskbar shortcut pointing to wrong .exe

[ndonkoHenri]

• Taskbar fix: When a packed Flet app runs on Windows, it spawns flet.exe (the Flutter client) as a child process. Windows associates the taskbar entry with the child's executable path (~/.flet/client/.../flet.exe), so pinning the app creates a shortcut to the bare client. The fix sets a Windows AppUserModelID on flet.exe via the FLET_APP_USER_MODEL_ID environment variable, so Windows associates the taskbar entry with the parent application instead. Resolves Blank White Screen When Launching Flet App from Taskbar After Initial Launch #5151.
  

• Pack bundling fix: flet pack was copying the extracted client files into the PyInstaller bundle, but at runtime ensure_client_cached() looks for an archive (flet-windows.zip / flet-linux-*.tar.gz). The archive was never found, so the app always fell back to downloading from GitHub on first launch — wasteful for released versions, broken for unreleased ones. macOS already re-packed correctly; Windows and Linux now do the same.

Testable CI artifacts: https://github.com/flet-dev/flet/actions/runs/24243238835

Summary by Sourcery

Ensure packed Flet desktop apps bundle and launch the correct client archives across platforms and integrate with Windows taskbar pinning behavior.

Bug Fixes:

• Fix Windows taskbar pinning so packed Flet apps are associated with the parent executable instead of the cached flet.exe client.
• Ensure flet pack bundles the desktop client as an archive (zip/tar.gz) that matches ensure_client_cached() expectations on Windows and Linux, avoiding fallback network downloads.

Enhancements:

• Expose a public get_artifact_filename() helper for determining the platform-specific desktop client archive name.
• Improve pack command behavior by compressing patched client binaries into platform-appropriate archives before PyInstaller runs.
• Clarify desktop client and environment-variable documentation strings in flet_desktop.

[sourcery-ai]

We've reviewed this pull request using the Sourcery rules engine

[Copilot]

Pull request overview

This PR improves flet pack-produced desktop apps by (1) ensuring the bundled Flutter client archive is actually discoverable at runtime (avoiding first-run downloads), and (2) fixing Windows taskbar pin/shortcut behavior by setting an AppUserModelID for the spawned flet.exe process (resolving #5151).

Changes:

• Expose and use a shared artifact naming function so flet pack can bundle the exact archive name ensure_client_cached() expects.
• Re-compress the patched client directory into a platform-appropriate archive during flet pack (Windows .zip, Linux .tar.gz; macOS already repacks).
• Add Windows AppUserModelID plumbing: Python sets FLET_APP_USER_MODEL_ID, and the Windows runner reads it and calls SetCurrentProcessExplicitAppUserModelID().

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
sdk/python/packages/flet-desktop/src/flet_desktop/init.py	Adds get_artifact_filename() and sets FLET_APP_USER_MODEL_ID in the child process env on Windows.
sdk/python/packages/flet-cli/src/flet_cli/commands/pack.py	Re-compresses the copied flet/ client directory into the runtime-expected archive format/name during packaging.
client/windows/runner/main.cpp	Reads FLET_APP_USER_MODEL_ID and sets the process AppUserModelID to fix taskbar association/pinning.

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[Copilot]

from flet_desktop import get_artifact_filename is executed at module import time, but handle() only installs/ensures flet-desktop later via ensure_flet_desktop_package_installed(). In an environment where flet-desktop isn't installed yet, flet pack will fail before it can run the installer. Consider moving the flet_desktop import into handle() (after the ensure call) or importing lazily only inside the Linux branch with a clear error if unavailable.

Suggested change

	from flet_desktop import get_artifact_filename
	def get_artifact_filename(*args, **kwargs):
	from flet_desktop import get_artifact_filename as _get_artifact_filename
	return _get_artifact_filename(*args, **kwargs)

[FeodorFitsner]

Add changelog record.