Add compilerOptions group to bsconfig.json

[markwpearce]

Summary

Introduces a dedicated compilerOptions object in bsconfig.json for options that control how BrighterScript interprets, validates, and compiles code — similar to TypeScript's compilerOptions — as opposed to top-level options that control project structure, file discovery, and tooling/reporting behavior.

Closes #1734

• The following options move into compilerOptions: allowBrighterScriptInBrightScript, autoImportComponentScript, bslibDestinationDir, emitDefinitions, emitFullPaths, legacyCallfuncHandling, manifest, minFirmwareVersion, pruneEmptyCodeFiles, relativeSourceMaps, removeParameterTypes, resolveSourceRoot, sourceMap, sourceRoot, strict, strictCallFunc, strictNodeMembers.
• Legacy top-level locations still work for backwards compatibility. If an option is set both at the top level and in compilerOptions, the compilerOptions value wins.
• Using a deprecated top-level option loaded from an actual bsconfig.json file (including through an extends chain) now emits a deprecated-bsconfig-option warning diagnostic pointing at the compilerOptions equivalent. This is deliberately scoped to file-based config — options passed programmatically to Program/ProgramBuilder are not flagged, since that's direct API usage rather than bsconfig.json authoring.
• compilerOptions deep-merges across an extends chain (matching TypeScript's behavior), unlike every other bsconfig key, where a child's value fully replaces the parent's.
• Updated bsconfig.schema.json, docs/bsconfig.md, and the README.md example accordingly.

This is a first pass at the field list — the set of options that belongs in compilerOptions vs. top-level is intentionally open to discussion, per the linked issue.

Test plan

• npm run build
• npm run lint
• npm run test:nocover (4271 passing)
• New unit tests covering: precedence (compilerOptions wins over legacy), deep-merge across extends, deprecation warning scoped to file-loaded config only (not programmatic API usage), and end-to-end diagnostic surfacing through ProgramBuilder

Note

This PR was mostly written by Claude (Anthropic's Claude Code), working from a design discussion with @markwpearce. Flagging for reviewer awareness — please review as you would any other contribution.

🤖 Generated with Claude Code

[markwpearce]

FYI for reviewers: I checked how much of the existing test suite uses the legacy flat bsconfig option names (sourceMap, strict, minFirmwareVersion, manifest, etc.) directly on options objects passed to Program/ProgramBuilder.

• 24 spec files, 112 occurrences use the legacy flat names — heaviest: Program.spec.ts (33, almost all sourceMap: true), bscPlugin/validation/ProgramValidator.spec.ts (10), bscPlugin/validation/BrsFileValidator.spec.ts (9), files/BrsFile.spec.ts (7).
• None of these trip the new deprecated-bsconfig-option warning, since the warning is scoped to options loaded from an actual bsconfig.json file (including via extends) — not options passed programmatically to Program/ProgramBuilder. That scoping was actually driven by this exact pattern: an earlier version of this PR warned unconditionally and broke ~50 tests that construct Program/ProgramBuilder with plain option objects like { rootDir, sourceMap: true }.
• So no test changes were needed for this PR to land, but if we ever want the test suite itself to model the new compilerOptions style, it's a real but mostly mechanical chunk of work (sourceMap: true → compilerOptions: { sourceMap: true }), concentrated in a handful of files.

Not blocking — just flagging for context/possible follow-up.

[markwpearce]

Building using this change shows warnings like this:

...
[04:07:09:929 PM] DiagnosticsManager.getDiagnostics()
[04:07:09:930 PM] diagnostic counts: total=81, after filter=77
[04:07:09:931 PM] DiagnosticsManager.getDiagnostics() finished. (1.422ms)

bsconfig.json:1:1 - warning deprecated-bsconfig-option: 'autoImportComponentScript' is deprecated at the top level of bsconfig.json. Move it into 'compilerOptions.autoImportComponentScript' instead

bsconfig.json:1:1 - warning deprecated-bsconfig-option: 'sourceMap' is deprecated at the top level of bsconfig.json. Move it into 'compilerOptions.sourceMap' instead

[04:07:09:932 PM] Building
....