Add Windows prompt template library, apply, save, and detach workflow

[coneilen]

Summary

• add a native Windows prompt-template library that reads project and per-user Markdown templates, searches them from an explicit node-form action, and deterministically fills the typed node draft
• preserve New Loop's default path to the node form even when saved templates exist, matching the macOS Templates control
• add Save as Template and followed-template Detach actions with typed daemon encoding
• cover template application, template-follow detection, detach wire format, WindowsShell contracts, and the explicit picker path in the UIA gate

Validation

RED: git show a6ada6a:graphcode-windows/src/App.zig -> A saved per-user template forced the picker before Create or edit node, so the default New Loop flow did not reach the node form.
GREEN: zig-0.15.2\zig.exe test src\TemplateLibrary.zig -> 61 template library and imported form tests passed, including deterministic goal and timed draft prefill.
GREEN: zig-0.15.2\zig.exe build -Dwinghostty-dir=..\.graphcode-tools\providers\winghostty -Doptimize=ReleaseSafe -> Windows ReleaseSafe shell build passed.
GREEN: pwsh -NoProfile -File Tools\windows\uia-live-gate.ps1 -Shell graphcode-windows\zig-out\bin\graphcode-windows.exe -> New Loop opened Create or edit node, explicit Templates opened the picker, and Enter returned to the node form before the later local toolbar assertion.
REGRESSION: pwsh -NoProfile -File Tools\windows\Tests\WindowsShell.Tests.ps1 -ZigExecutable $env:GRAPHCODE_ZIG0152 -> 97 Windows shell contract tests passed with the pinned Winghostty headers.
REGRESSION: pwsh -NoProfile -File Tools\windows\Tests\ValidationRunner.Tests.ps1 -> validation runner passed.

UI Automation regression resolved

The failed clean-runner windows-shell job established that the mandatory picker was this change's regression: its foreground diagnostics showed Choose a saved template while the existing empty-global New Loop scenario waited for Create or edit node. The shell remained alive and emitted UIA wait diagnostics; this was not the toolbar assertion or a shell crash.

The fix follows macOS: New Loop always opens the node form, and a saved-template library is available only from that form's explicit Templates action. The UIA scenario now proves the default form appears first, invokes the stable native Templates command, opens Choose a saved template, accepts with Enter, and returns to the form. The local interactive run next reaches the previously observed toolbar assertion, after the template workflow has completed; clean CI will revalidate that independent later gate.