DEV-1833: Align app dictation JS API documentation

[tonytlwu]

Summary

• Align Fliplet.AI.transcribeAudio(audio, options) documentation with the completed runtime contract for Blob and File inputs.
• Document supported models, exact { text } response, 25 MiB inclusive limit, accepted MIME types, optional-undefined semantics, cancellation, timeout, provider-handoff billing, and error handling.
• Keep the runnable MediaRecorder example with microphone cleanup and cancellation.
• Remove aiProvider from the documented AI API contract and update model-only Gemini examples.
• Regenerate the agent discovery outputs.

Jira

DEV-1833

Related API PR

Fliplet/fliplet-api#8586

Acceptance mapping

• AC-006: docs/API/core/ai.md matches the implemented API for input types, model selection, MIME support, exact limit, cancellation/deadline behavior, charging after provider handoff, response shape, and cleanup.
• Omitted or explicitly undefined optional values use defaults; invalid explicit values reject.
• The public contract returns exactly { text }; provider usage remains internal for metering.
• The generated llms-full.txt and V3 library catalog reflect the canonical page.

QA sample before documentation deployment

Until this PR is merged and published, QA must copy the runnable sample from docs/API/core/ai.md at this PR's pinned head SHA, 683d3d59e2e0b6ec196338506800b1bcf627ded5. The live developer documentation is not a valid source for the updated sample until deployment is verified.

Add that exact sample to the V3 QA app and test real microphone record/stop, result.text rendering, microphone release on success/failure/recording cancellation/upload cancellation, and the deployed API behavior from #8586.

Verification

From an archive of the final source tree:

• npm run test:unit — 163 passed, 0 failed.
• node bin/build-agent-indexes.mjs --strict — passed.
• bundle exec jekyll build — passed; only unrelated existing Liquid warnings remain.
• node bin/copy-md-siblings.mjs and source/rendered comparisons — passed.
• Canonical, generated, sibling, and rendered AI docs contain zero aiProvider references.
• git diff --check passes and the worktree is clean.

Merge and publication gate

This PR targets the DEV-1833 project branch as requested. Do not publish the documentation until API PR #8586 has been deployed to production and the served core asset has been verified. Until then, QA should continue using this PR as the sample-code source.