Update roslyn to 5.12.0-1.26461.1

[dibarbet]

Official Roslyn build: 20260911.1 (build 3072922)

View Complete Diff of Changes

• Fix compiler server logging (PR: #85193)
• Follow-up to telemetry collection PR (PR: #85254)
• Version EditorConfig VS components independently (PR: #85250)
• Fix type hierarchy request test compilation (PR: #85253)
• Avoid unnecessary argument-builder work in generic type substitution (PR: #85230)
• Track per-project load completion in LanguageServerProjectLoader (PR: #85107)
• Simplify partial modifier lookahead naming (PR: #85183)
• LSP 3.18 protocol updates (PR: #82294)
• Add empty result to LSP request telemetry (PR: #85082)
• Ignore embedded debug format for metadata-only emit (PR: #85028)
• Add an instruction to link the plan/session in the PR (PR: #85235)
• Use locally built CodeAnalysis testing libraries (PR: #85215)
• Forward DOTNET_ROOT and DOTNET_HOST_PATH to BuildHost (PR: #85195)
• Consolidate roslyn options to build with analyzers (PR: #85227)
• Make the ProjectData.Tasks package packable and include the targets file (PR: #85232)
• Make RoslynTelemetry instance-based with an ambient Current (PR: #85151)
• Use non-null initial state for null-resilient properties in constructors (PR: #84991)
• Show progress during long code reviews (PR: #85233)
• Reduce decl/impl split fallbacks: split header-directive and @Inject components (PR: #85069)
• Honor inherited AssetPath attributes on component parameters (PR: #85171)
• Make Razor tag helper resolution safe for concurrent mixed inputs (PR: #85167)
• Let F# take part in the Navigate To search that runs while the solution loads (PR: #85213)
• Let F# create a workspace project context without blocking the main thread (PR: #85219)
• Fix FBA restore mismatch issue (PR: #85204)
• Expose registered project file extensions (PR: #85106)
• Classify parameter discards earlier, syntactically instead of semantically, resolving classification conflict (PR: #85225)
• Migrate Microsoft.NET.ProjectData.Tasks and the associated tests (PR: #85154)
• Correct stale Roslyn guidance references (PR: #85211)
• Trigger CI on PRs to dev/* branches (PR: #85216)
• Remove instructions causing unecessary updates to instructions files (PR: #85214)
• Test for line endings and long paths (PR: #85127)
• Include NuGet.config in Helix test payloads (PR: #85210)
• Fix missing PDBs in Editorconfig DLLs (PR: #85192)
• Centralize Language Server workspace folder tracking (PR: #85105)
• Delete the DiagnosticsToolWindow (PR: #85152)
• Import EditorConfig templates from dotnet/templates (PR: #85157)
• Improve parser recovery for misplaced 'partial' modifiers (PR: #83216)
• Add instructions for how to build with analyzers (PR: #83228)
• Make VB SDK samples strict (Option Strict On) (PR: #85124)
• Sync FBA sources (PR: #85065)
• Record partial lambda parsing baselines (PR: #85166)
• Visit left operand conversion in a fast path of nullable analysis (PR: #85115)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 8742256 (PR: #799)
• Fix EditorConfig at solution level (PR: #782)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 6347393 (PR: #678)
• enable nullable (PR: #692)
• Fix a NullReferenceException in the DeclarePublicAPI analyzer (PR: #677)
• Merge pull request Have a keyboard shortcut for the yellow bulb options (help) #644 from jmarolf/features/update-default-editorconfig-settings (PR: #644)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 4901452 (PR: #511)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 4901402 (PR: #510)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 4900535 (PR: #509)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 4905189 (PR: #512)
• Set VSSDKTargetPlatformRegRootSuffix (PR: #461)
• Update VS SDK (PR: #487)
• Update VSSDK (PR: #479)
• Localized file check-in by OneLocBuild Task: Build definition ID 10077: Build ID 4718492 (PR: #478)
• Fix Editor config issues (PR: #206)
• fix EditorConfig templates names (PR: #193)
• Fix vs dev (PR: #134)
• Add new classlib templates (PR: #132)
• do not build tasks and use nuget package instead (PR: #92)
• move-to-arcade (PR: #90)
• Correcting two option names
  (PR: #83)
• Trim trailing whitespace in EditorConfig item templates (PR: #73)
• Update editorconfig default name (PR: #65)
• Fix access to resources (PR: #64)
• LOC CHECKIN | dotnet/templates master | 20180629 (PR: #61)
• adding VB editorconfig templates (PR: #56)
• Merge dev15.8 preview2 to master (PR: #55)
• fix setup (PR: #54)
• Merges/dev15.8 preview2 to master (PR: #52)
• Update setup authoring (PR: #50)
• Merges/dev15.7.x to dev15.8 preview2 (PR: #48)
• reset to defaults (PR: #47)
• Fix aspnet node order (PR: #46)
• Merges/dev15.8 preview2 to master (PR: #45)
• Refactor (PR: #44)
• update vb authoring (PR: #41)
• adding localized resources (PR: #40)
• fixing Kaseys comments (PR: #39)
• Editorconifg changes (PR: #38)

[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved review issues were identified.

Review tier: Lite
Findings: None

What changed in this PR

Updates the C# extension to Roslyn 5.12.0-1.26461.1 and documents user-facing improvements.

Changes:

• Bumps the default Roslyn version.
• Adds filtered Roslyn changes to the changelog.

File	Description
package.json	Updates the Roslyn version pin.
CHANGELOG.md	Documents the Roslyn update and related improvements.

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