fix: publish source files referenced by source conditional exports

[Tyagiquamar]

Closes #10397

Intent

react-aria, react-stately, and react-aria-components advertise a source conditional export (./exports/index.ts, ./exports/*.ts), but their published files excluded exports/** (and src/**, which the export shims re-export from). Any bundler opting into the source condition — e.g. Vite with resolve.conditions: ['source'], common in Storybook setups — resolves an entry that is absent from the installed package and fails with Failed to resolve import "react-aria/…".

Why this approach

Two options from the issue: drop the source condition, or publish the sources. Dropping it is not viable here: the monorepo itself resolves workspace packages through the source condition (customConditions: ["source"] in tsconfig.json / tsconfig.build.json), and every sibling package (@react-stately/*, @internationalized/*, @react-types/shared with no files allowlist at all) already publishes the sources its source condition points at. So this aligns the three outliers with the repo convention by removing the !exports/** and !src/** exclusions. I verified nothing under src//exports/ imports from the still-excluded dirs (stories, test, docs, example, intl), so the published sources are self-contained apart from workspace deps that already ship their own source.

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices
• I understand every change in this PR and can explain why it's there.
• If AI-assisted, I followed our AI contribution guidance and pointed my assistant at CLAUDE.md.

No unit tests apply (packaging metadata only); verification below stands in for them. Accessibility practices do not apply (no component or interaction change).

AI disclosure: an AI assistant (Muse Spark, pointed at AGENTS.md per the contribution guide) helped investigate and verify; I reviewed the diff, confirmed the root cause against the published tarball layout, and own the change and follow-ups.

📝 Test Instructions:

• npm pack --dry-run in packages/react-aria (and the other two): exports/*.ts and src/** are now listed, stories/**/test/** still excluded, tarball stays small (~339 kB packed for react-aria).
• Simulate an installed package (package.json + exports/ + src/), then node --conditions=source -e "require.resolve('react-aria'); require.resolve('react-aria/I18nProvider')": both resolve to the .ts sources with the fix, and fail with MODULE_NOT_FOUND without it (matching the reported Vite failure).

🧢 Your Project:

Independent contributor; using React Aria with Vite + source conditions.