Improve extension AppHost output handling and CodeLens anchors

[adamint]

Description

Improves several extension-only AppHost UX paths without requiring CLI or hosting changes:

• Buffers Aspire CLI stdout/stderr by line in the debug session so partial chunks do not split output across debug-console lines.
• Sets CLI child-process stdout/stderr encoding to UTF-8 so multi-byte characters are preserved across chunk boundaries.
• Stops prefixing every stderr line with ❌; CLI/Spectre error output already includes the appropriate prefix, while benign stderr messages such as update notifications should not be labeled as failures.
• Avoids an infinite aspire describe --follow restart loop when the follow process exits before producing data.
• Anchors CodeLens state/actions for single-resource fluent chains at the statement start, while preserving per-call anchoring for multi-resource chains.

Validation:

• npm run compile-tests
• npm run unit-test | grep -A3 "AspireCodeLensProvider resource lens anchoring"

Fixes # (issue)

Checklist

• Is this feature complete?
  • Yes. Ready to ship.
  • No. Follow-up changes expected.
• Are you including unit tests for the changes and scenario tests if relevant?
  • Yes
  • No
• Did you add public API?
  • Yes
    • If yes, did you have an API Review for it?
      • Yes
      • No
    • Did you add <remarks /> and <code /> elements on your triple slash comments?
      • Yes
      • No
  • No
• Does the change make any security assumptions or guarantees?
  • Yes
    • If yes, have you done a threat model and had a security review?
      • Yes
      • No
  • No
• Does the change require an update in our Aspire docs?
  • Yes
    • Link to aspire.dev issue:
      • New issue
  • No

[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/microsoft/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 16799

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/microsoft/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 16799"

[Copilot]

Pull request overview

This PR improves Aspire VS Code extension UX around (1) workspace aspire describe --follow watching behavior, (2) debug-session CLI output rendering, and (3) CodeLens anchoring for fluent resource declarations—without requiring any CLI/hosting changes.

Changes:

• Prevents an infinite restart loop when aspire describe --follow exits without producing any data (common when no AppHost is running / --follow unsupported).
• Buffers Aspire CLI stdout/stderr by line in debug sessions (and forces UTF-8 decoding) to avoid chunk-splitting issues and corrupted multi-byte characters; stops adding an extra “❌” prefix to every stderr line.
• Adjusts CodeLens anchoring logic so single-resource fluent chains anchor at the statement start, while multi-resource chains keep per-call anchoring; adds unit tests for this behavior.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
extension/src/views/AppHostDataRepository.ts	Stops quietly (no auto-restart) when describe --follow exits without producing data; keeps backoff restart only for previously-working streams.
extension/src/debugger/languages/cli.ts	Sets stdout/stderr stream encoding to UTF-8 and passes decoded string chunks through callbacks.
extension/src/debugger/AspireDebugSession.ts	Adds per-stream line buffering + exit-time flush; removes blanket stderr “❌” prefixing and preserves chunk integrity.
extension/src/editor/AspireCodeLensProvider.ts	Updates resource CodeLens anchor selection based on whether resources share the same statement start.
extension/src/test/aspireCodeLensProvider.test.ts	Adds mocha types reference and unit tests validating CodeLens anchoring behavior for single- vs multi-resource fluent chains.

[adamint]

Superseded by #16795, which now includes this focused slice.