chore: update message annotations terminology to include appends

[matt423]

Description

Updates all instances of "Message updates, deletes and annotations" and similar phrases throughout the documentation to include "appends".

Changes include:

• Updated channel rule names from "Message annotations, updates, and deletes" to "Message annotations, updates, deletes, and appends"
• Updated API documentation descriptions for serial fields
• Updated example code comments and error messages
• Updated error code descriptions and resolutions

Review App

Checklist

• Commits have been rebased.
• Linting has been run against the changed file(s).
• The PR adheres to the writing style guide and contribution guide.

Summary by CodeRabbit

• Documentation
  • Updated channel rules documentation to reflect expanded requirements for message operations. The "Message annotations, updates, and deletes" rule now includes "appends" as an additional required channel rule for serial field population and related message features across API docs, SDKs, and error codes.

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Walkthrough

Documentation updates across the codebase to reflect expanded channel rule requirements. The rule "Message annotations, updates, and deletes" is updated to "Message annotations, updates, deletes, and appends" across type definitions, API references, feature guides, examples, and error documentation to indicate that appends must also be enabled for related functionality.

Changes

Cohort / File(s)	Summary
Type and Field Definitions content/partials/types/_message.textile, src/pages/docs/api/realtime-sdk/channels.mdx, src/pages/docs/api/realtime-sdk/messages.mdx, src/pages/docs/api/rest-sdk/channels.mdx, src/pages/docs/messages/index.mdx	Updated serial field documentation to require appends be enabled alongside annotations, updates, and deletes in channel rules for the field to be populated.
REST and Transport API References src/pages/docs/api/rest-api.mdx, src/pages/docs/ai-transport/features/token-streaming/message-per-response.mdx	Updated channel rule prerequisites for message endpoints and token streaming to include appends in the required rule set.
Feature and Message Guides src/pages/docs/channels/index.mdx, src/pages/docs/chat/integrations.mdx, src/pages/docs/messages/annotations.mdx, src/pages/docs/messages/updates-deletes.mdx	Updated channel rule labels and descriptions across message annotations, updates/deletes, and channel configuration sections to include appends as an enabled capability.
JavaScript Example Code and Documentation examples/pub-sub-message-annotations/javascript/README.md, examples/pub-sub-message-annotations/javascript/src/config.ts, examples/pub-sub-message-annotations/javascript/src/script.ts	Updated comments, readme text, and error messages to reference the expanded channel rule name including appends.
Error Reference Documentation src/pages/docs/platform/errors/codes.mdx	Updated error code examples and descriptions to enumerate appends as a supported operation alongside message annotations, updates, and deletes.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~12 minutes

Poem

🐰 Appends now joins the ruleset's dance,
Annotations, updates, deletes—and advance!
Docs across the warren now sing,
Of serial identifiers and messages that spring. ✨

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The PR title accurately and specifically describes the main change: updating documentation terminology to include 'appends' in message annotation rules across all affected files.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate docstrings

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[matt423]

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✅ Actions performed

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