refactor: trim comments in the inline-script quick fix

[Stella Huang (StellaHuang95)]

Follow-up to #1788 (merged). That PR's comments were heavier than they needed to be; this trims them down to the handful that carry information the code does not.

No behavior change. Only comments and JSDoc are touched — 33 comment lines removed, 8 added back in condensed form, for a net reduction of 25.

What is kept, and why

Three comments survive because each documents a decision a reviewer would otherwise read as a bug:

• reportMissingModuleSource is in the unresolved-import code set. Pylance's own isMissingImportDiagnostic() excludes it, because for their change-spelling fix a stub-resolved module is correctly spelled. For us, "stub found but no source" means the package is not installed, which setting the environment up fixes. Reduced from a 6-line block to a trailing comment on the line itself.
• The routing metadata is reseeded after the save. Without it, a just-typed # /// script block gains its identity mid-create, which setUpInlineScriptEnvironment reads as a concurrent edit and silently skips the association. Reduced 3 lines to 2.
• promptUpdateExtensionsForInlineScripts() sits outside the try. The environment is already set up by that point, so a failure in the follow-up must not be surfaced to the user as a setup failure. Reduced 2 lines to 1.

The class-level JSDoc on InlineScriptSetupCodeActionProvider is kept at 3 lines — it still records that diagnostics and isPreferred are deliberately unset, which is the non-obvious part of the design.

What is removed

• The 6-line JSDoc over UNRESOLVED_IMPORT_DIAGNOSTIC_CODES.
• The 4-line JSDoc on isUnresolvedImportDiagnostic, condensed to one line.
• The 10-line class JSDoc, condensed to three.
• The provideCodeActions gating-order comment — the gate order is legible from the code.
• JSDoc on the two private helpers findOpenDocument and saveScriptBeforeSetup. The repo convention asks for docstrings on public functions; these are module-private.

Every exported symbol still carries a docstring, per .github/copilot-instructions.md.

Validation

• npm run lint — clean
• npm run compile-tests — clean
• npm run unittest — 2323 passing, 6 pending, 0 failing (unchanged from baseline)

The feature remains behind python-envs.inlineScripts.enabled, so nothing here is user-visible.

[Stella Huang (StellaHuang95)]

Closing for now - not ready to review yet.