Mac-on-Linux: implement launcher and search-equivalence lane for sourceos-shell

[mdheller]

Parent tracker: #77

Summary

Implement the launcher and search-equivalence lane required for the Mac-on-Linux realization of sourceos-shell.

Goal

Deliver launcher/search behavior that feels coherent under Mac-on-Linux constraints while preserving the explicit rollout invariants already captured in the Linux scaffolds:

• apps -> launcher or desktop-entry provider
• files -> Linux-native file search only
• web -> browser/web agent
• no redundant file search for files

Existing upstream anchors

Relevant already-open work includes:

• #16 — temporary Albert bridge tracking
• #72 — search-provider scaffold and invariant config
• #73 / #76 — service-graph grouping and checks

Workstreams

1. Command surface

• command-palette expectations
• launcher parity vs shell-native search behavior
• transition from bridge mode to shell-native mode

2. Provider policy

• Linux-native file provider selection
• provider disclosure and debugging surfaces
• exact invariant enforcement for no redundant search

3. Validation

• fixture queries for apps/files/web
• logs and acceptance checks proving single-provider routing
• migration criteria for retiring the bridge

Acceptance criteria

• launcher/search goals are explicitly documented
• bridge mode vs shell-native mode is described
• provider-policy and invariant work are separated and trackable
• follow-on PRs can reference this issue for launcher/search work

Proposed owner

@mdheller