Add shared Windows.UI.Shell.Tasks (Forerunner) integration to SDK crate

Factor the common Rust integration with the experimental
Windows.UI.Shell.Tasks ("Forerunner" / taskbar presence) API, previously
duplicated between the Copilot desktop app (github/github-app) and the CLI
(github/copilot-agent-runtime), into the github-copilot-sdk crate so both
products can consume one implementation.

New `shell_tasks` module under `rust/src/shell_tasks/`, behind the
off-by-default `shell-tasks` Cargo feature:
- `contract`: verbatim copy of the CLI `taskbar-contract` crate. Pure-std,
  FFI-free contract for the hover-card round-trip (named-pipe name, focus
  sidecar file name, sidecar payload format) with its unit tests.
- `bindings`: verbatim copy of the CLI vendored WinRT projection of
  AppTaskContract, re-exported as `Windows`. Gated on `#[cfg(windows)]`.

The `windows`/`windows-core` deps are optional and Windows-only (declared
under [target.'cfg(windows)'.dependencies]), activated only by the
`shell-tasks` feature, mirroring how `bundled-cli` gates its optional `zip`
dep. Non-Windows and feature-off builds pull neither crate.

Verified on Windows: default `cargo check` plus `cargo
build/test/clippy/doc --features shell-tasks` all green (contract unit
tests pass).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 67c6593a-bb90-4106-a143-49c19fa32a0d

Add shared AppTaskContent builder to shell_tasks module

Extract the WinRT AppTaskContent call sequence that the Copilot desktop
app and CLI implement identically into a neutral, data-driven builder.

The new content module exposes a cross-platform ContentSpec/ContentBody
data model plus #[cfg(windows)] build_content/make_uri/make_result_asset
helpers that faithfully reproduce both products' WinRT sequences
(CreateSequenceOfSteps, CreatePreviewThumbnail, CreateTextSummaryResult,
CreateGeneratedAssetsResult, SetQuestion, AddButton, SetTextInput,
AppTaskResultAsset::CreateInstance). Product-specific preparation
(template dispatch, asset caps, file:// resolution, deep-link building)
stays in each adapter, which hands the builder an already-resolved spec.

Feature-gated behind shell-tasks; 4 new unit tests (15 total).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 67c6593a-bb90-4106-a143-49c19fa32a0d

Add shared sparse-package identity registrar to shell_tasks

Factor the WinRT sparse (external-location) package registration routine
out of the CLI's napi bridge into a napi-free shell_tasks::sparse module
so both the CLI and the desktop app can share one implementation.

The module exposes plain synchronous, #[cfg(windows)] functions
(register_sparse_package, deregister_sparse_package,
current_package_family_name) plus the process-lifetime MTA keepalive
(ensure_process_mta) that guards windows-rs's cached activation
factories against the 0xC0000005 fault. Neutral result types
(RegisterOutcome, SparseError) compile on every platform. Each product
wraps these in its own async surface (CLI napi AsyncTask; app
spawn_blocking/Tauri) and keeps its own AppxManifest and registration
trigger.

Adds ApplicationModel/Management_Deployment/Win32_System_Com to the
Windows-only optional windows dep. Feature-gated behind shell-tasks;
2 new cross-platform tests (19 total).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 67c6593a-bb90-4106-a143-49c19fa32a0d

Extract shell_tasks into standalone github-copilot-shell-tasks crate

Move the shared Windows.UI.Shell.Tasks integration out of the
github-copilot-sdk client crate into a standalone, build.rs-free
workspace member at rust/crates/github-copilot-shell-tasks so it can be
consumed by the CLI's napi addon (and the desktop app's Tauri backend)
without dragging in the full SDK client dependency tree or its
network-touching build.rs.

- New crate github-copilot-shell-tasks (lib github_copilot_shell_tasks)
  owns contract/content/sparse/bindings; only deps are the Windows-only
  windows/windows-core crates, gated under cfg(windows).
- rust/Cargo.toml becomes the workspace root; the shell-tasks feature now
  pulls the optional path dep, and the client re-exports it as
  github_copilot_sdk::shell_tasks. windows/windows-core deps moved to the
  new crate.

Validated on Windows: standalone crate builds with no download and no
warnings; 17 tests pass; clippy/doc clean; client builds/docs with
--features shell-tasks; default (feature-off) check unaffected.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 67c6593a-bb90-4106-a143-49c19fa32a0d

Re-export windows/windows-core from shell-tasks crate for island consumers

Add `pub use ::windows;` and `pub use ::windows_core;` (both `#[cfg(windows)]`)
to the `github-copilot-shell-tasks` crate root so a consumer that adopts the
crate as an isolated WinRT island (the desktop app's Tauri backend, pinned to
an older `windows` via Tauri/wry) can funnel all of its Windows.UI.Shell.Tasks
call-sites and the supporting WinRT types (Foundation::Uri,
ApplicationModel::Package, Win32::System::Com, HSTRING) through the exact
`windows` 0.62 version the projection was generated against, without declaring
its own conflicting `windows` dependency.

Crate build, clippy, and 17 unit tests pass; the client crate still builds with
the `shell-tasks` feature.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 67c6593a-bb90-4106-a143-49c19fa32a0d

Author: devGIT28

rust/Cargo.lock

@@ -27,12 +27,25 @@ include = [
 [lib]
 name = "github_copilot_sdk"
 
+# This manifest is both the root package and the workspace root. The standalone
+# `github-copilot-shell-tasks` crate is a member so it builds/tests with the
+# workspace and can be depended on by path above.
+[workspace]
+members = ["crates/github-copilot-shell-tasks"]
+resolver = "3"
+
 [features]
 default = ["bundled-cli"]
 bundled-cli = ["dep:tar", "dep:flate2", "dep:zip"]
 bundled-in-process = ["bundled-cli", "dep:libloading"]
 derive = ["dep:schemars"]
 test-support = []
+# Shared `Windows.UI.Shell.Tasks` ("Forerunner" / taskbar presence) integration,
+# re-exported as the `shell_tasks` module. Off by default to keep the base SDK
+# lean. Enabling it pulls the standalone, build.rs-free
+# `github-copilot-shell-tasks` crate (its `windows` / `windows-core` deps only
+# activate on Windows), mirroring how `bundled-cli` gates its optional `zip`.
+shell-tasks = ["dep:github-copilot-shell-tasks"]
 
 # Build docs.rs documentation with all features so feature-gated APIs
 # (e.g. `define_tool`, `schema_for`) appear and intra-doc links resolve.
@@ -59,6 +72,10 @@ getrandom = "0.2"
 uuid = { version = "1", default-features = false, features = ["v4"] }
 flate2 = { version = "1", optional = true }
 tar = { version = "0.4", optional = true }
+# Shared Windows.UI.Shell.Tasks integration, re-exported as `shell_tasks` behind
+# the `shell-tasks` feature. Standalone + build.rs-free so enabling it does not
+# perturb the base SDK; its Windows-only WinRT deps activate only on Windows.
+github-copilot-shell-tasks = { version = "0.0.0-dev", path = "crates/github-copilot-shell-tasks", optional = true }
 # LLM inference callback transport: idiomatic HTTP/WebSocket forwarding for the
 # `CopilotRequestHandler`, plus base64/byte/stream plumbing for the chunk protocol.
 base64 = "0.22"

rust/Cargo.toml

@@ -0,0 +1,34 @@
+[package]
+name = "github-copilot-shell-tasks"
+version = "0.0.0-dev"
+edition = "2024"
+rust-version = "1.94.0"
+description = "Shared Windows.UI.Shell.Tasks (Forerunner / taskbar presence) integration for GitHub Copilot, consumable by the desktop app and CLI without the full SDK client."
+keywords = ["copilot", "github", "windows", "taskbar", "forerunner"]
+categories = ["os::windows-apis", "api-bindings"]
+repository = "https://github.com/github/copilot-sdk"
+homepage = "https://github.com/github/copilot-sdk"
+license = "MIT"
+
+[lib]
+name = "github_copilot_shell_tasks"
+
+# Intentionally lightweight: no build.rs, and the only dependencies are the
+# Windows-only WinRT crates. This lets a napi addon (CLI) or Tauri backend (app)
+# depend on the shared integration without dragging in the `github-copilot-sdk`
+# client crate (JSON-RPC, tokio, and its network-touching build.rs).
+[dependencies]
+
+# `Foundation` covers the projection's `DateTime`/`IReference`/`Uri`;
+# `ApplicationModel` + `Management_Deployment` + `Win32_System_Com` back the
+# sparse-identity registrar (`sparse`); `windows-core` provides the WinRT
+# runtime. Declared under `cfg(windows)` so non-Windows builds pull neither
+# crate and the whole crate compiles as a pure-`std` no-op.
+[target.'cfg(windows)'.dependencies]
+windows = { version = "0.62", features = [
+    "Foundation",
+    "ApplicationModel",
+    "Management_Deployment",
+    "Win32_System_Com",
+] }
+windows-core = "0.62"