Show issue_write MCP App form for labels/assignees/milestone/type

[mattdholloway]

Problem

The issue_write tool decides whether to render the MCP App form or execute directly via the issueWriteFormParams allow-list: a call carrying any parameter outside that set bypasses the form (so the model-supplied values aren't silently dropped on form re-submit).

But the issue-write MCP App form actually prefills from toolInput and re-submits labels, assignees, milestone, and type (ui/src/apps/issue-write/App.tsx lines 874–957, 1012–1023). Those four were missing from issueWriteFormParams, so passing any of them made issueWriteHasNonFormParams return true and skipped the confirmation form — precisely in the cases where the form is most useful. This left the gating logic out of sync with what the UI supports (issue_fields, which the form handles identically, was already in the allow-list — the asymmetry confirms the list was simply stale).

The PR forms (create_pull_request, update_pull_request) were already aligned, so no gating change there.

Fix

• Add labels, assignees, milestone, type to issueWriteFormParams. The allow-list now covers every input-schema property, so issueWriteHasNonFormParams becomes a forward-compatibility safety net (trips only for a future schema property not yet wired into the form).
• Correct the now-inaccurate show_ui guidance on both issue_write and create_pull_request. Both descriptions claimed the form "does not collect" fields it actually collects (labels/assignees/milestone/type/issue_fields for issues; reviewers for PRs). The PR gating was already correct — only its description text was misleading.
• Update the stale issueWriteHasNonFormParams comment and the Test_issueWriteSchemaClassification knownNonForm allow-list.

Tests / generated files

• Updated Test_issueWriteHasNonFormParams, Test_issueWriteSchemaClassification, and the Test_IssueWrite_MCPAppsFeature_UIGate labels subtest (labels now routes through the form).
• Regenerated toolsnaps (issue_write, create_pull_request) and docs (feature-flags.md, insiders-features.md). README is unchanged because show_ui is stripped from the non-UI schema it renders.
• script/lint clean, script/test (race) passing.

No behavior change for non-UI clients or for the PR tools' execution paths.

[Copilot]

Pull request overview

This pull request aligns the issue_write MCP App UI gating logic with what the issue-write UI form actually supports, ensuring the confirmation form is shown (and prefills/resubmits correctly) when callers provide labels/assignees/milestone/type. It also updates show_ui guidance text for both issue_write and create_pull_request to remove now-misleading “form does not collect …” examples.

Changes:

• Expand issueWriteFormParams to include labels, assignees, milestone, and type, so those inputs no longer force bypassing the MCP App form.
• Update show_ui descriptions for issue_write and create_pull_request to reflect current UI form capabilities.
• Update tests, toolsnaps, and generated docs to match the new gating behavior and updated descriptions.

Show a summary per file

File	Description
pkg/github/pullrequests.go	Updates create_pull_request show_ui description to remove misleading “form does not collect reviewers” guidance.
pkg/github/issues.go	Adds labels/assignees/milestone/type to the UI allow-list and updates issue_write show_ui description + gating commentary.
pkg/github/issues_test.go	Adjusts UI-gating tests and schema-classification guardrails for the expanded form parameter set.
pkg/github/toolsnaps/issue_write.snap	Regenerated snapshot reflecting the updated show_ui description.
pkg/github/toolsnaps/create_pull_request.snap	Regenerated snapshot reflecting the updated show_ui description.
docs/insiders-features.md	Regenerated docs reflecting updated show_ui descriptions.
docs/feature-flags.md	Regenerated docs reflecting updated show_ui descriptions.

Copilot's findings

• Files reviewed: 7/7 changed files
• Comments generated: 0