Installable desktop builds and local runtime packaging

[ksamaschke]

Objective

Ship actual installable desktop application artifacts for supported platforms instead of packaging-plan placeholders.

In Scope

• Introduce real desktop packaging outputs for macOS, Windows, and Linux.
• Add app metadata, identity, icons, and version wiring required for packaged builds.
• Align local preview and packaged runtime startup behavior.
• Replace release expectations that stop at package-plan JSON artifacts.

Out of Scope

• Updater channel promotion and signing policy details beyond what packaging requires.
• QA certification signoff.

Acceptance Criteria

• CI produces runnable desktop artifacts for the supported matrix.
• Packaged startup path is exercised and testable.
• Packaging outputs replace metadata-only expectations in release validation.

Required Test Evidence

• RED: failing packaging and artifact-expectation tests.
• GREEN: passing package build validation for scoped targets.
• REFACTOR: green release validation after packaging cleanup.

Agent Profile Expected To Implement It

devops-engineer + developer

Tracking

• Type: story
• Priority: p1

Parent: #173

[ksamaschke]

Completed via #179/#180/#181 in dedicated packaging worktree. Desktop release outputs now use concrete platform artifact names across generation, checksum, signing, and release publication paths, with focused packaging and startup regression evidence captured on the child items.

[ksamaschke]

Closed via merge of PR #196 into dev.