docs: update spectrum-ts documentation for v12.5.0

[photon-action-bot]

Documentation Update: spectrum-ts v12.5.0

This PR updates documentation for spectrum-ts based on the v12.5.0 release.

Release Notes

New Features

• iMessage now surfaces inbound read receipts on app.messages: when someone reads a message your app sent, you’ll receive a read message with message.sender as the reader and message.content.target as your original outbound message.
• Read receipt targets are fully built Message objects, so you can inspect the original content and still use outbound affordances like edit() and unsend().
• readSchema is now exported from @spectrum-ts/core/authoring for callers that build or validate read content directly.

Improvement

• Read receipt docs are now much clearer, including DM vs group behavior, timestamp meaning, high-volume caveats, and examples for tracking who has read a message. 👀
• iMessage now reuses the same target-resolution path for reactions and read receipts, which improves cache behavior and avoids extra lookups when multiple events point at the same message.

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Version: 12.5.0

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🤖 This PR was auto-generated by Claude Code via the update-docs action in buildspace.

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Note

Low Risk
Dev-only dependency and lockfile refresh for documentation generation; no runtime app or security-sensitive code paths change in this diff.

Overview
Bumps the spectrum-ts dev dependency from 12.0.0 to 12.5.0 in package.json, with matching pnpm-lock.yaml updates so doc sync, type extraction, and vellum builds use the new SDK surface.

The lockfile also reflects transitive moves tied to that release (e.g. @spectrum-ts/* 12.5.0, @photon-ai/otel 3.3.0, @photon-ai/advanced-imessage 2.0.2 with explicit gRPC peers on the iMessage package). There are no authored doc or script changes in this diff—only the dependency pin.

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