docs(js-sdk): add Upload Files documentation

[PrajwalDhuleCC]

Description

• Add new "Upload Files & Send Attachments" guide documenting CometChat.uploadFiles() flow with per-file progress, cancel, and retry
• Add "Upload Files" page to JavaScript SDK Messaging section in docs.json
• Document Media Upload error category and specific error codes (ERR_INVALID_FILE_OBJECT, ERR_FILE_SIZE_EXCEEDED, ERR_FILE_COUNT_EXCEEDED, ERR_S3_UPLOAD_FAILED, ERR_PRESIGNED_URL_EXPIRED, ERR_UPLOAD_STALLED, ERR_UPLOAD_CANCELLED) in error-codes.mdx
• Update send-message.mdx to recommend upload-first pattern for multi-attachment composers and link to new upload guide
• Add CometChat.getMaxAttachmentCount() runtime API reference for checking attachment limits
• Clarify distinction between rejected (non-retryable) and failed (retryable) upload errors with MediaUploadListener callback mapping

Related Issue(s)

Type of Change

• Documentation correction/update
• New documentation
• Improvement to existing documentation
• Typo fix
• Other (please specify)

Checklist

• I have read the CONTRIBUTING document
• My branch name follows the naming convention
• My changes follow the documentation style guide
• I have checked for spelling and grammar errors
• All links in my changes are valid and working
• My changes are accurately described in this pull request

Additional Information

Screenshots (if applicable)

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Project	Status	Preview	Updated (UTC)
cometchat	🟢 Ready	View Preview	Jul 12, 2026, 7:53 PM

[raj-dubey1]

📋 Docs review — ✅ Approve

Reviewed this PR for docs-breakage and content accuracy, cross-checked against the implementing SDK PR cometchat-team/chat-sdk-javascript#568.

Verdict: Approve. Structurally safe and content-accurate — near-perfect.

✅ What passed

• Build safe: 0 unresolved nav refs; sdk/javascript/upload-files correctly added to JS SDK → Messaging in docs.json. Additive PR — no moves/renames, so no redirects needed. 0 orphans.
• API surface exact vs. chat-sdk-javascript#568: uploadFiles(), cancelFileUpload(), retryFileUpload(), clearUploadGroup(), getMaxAttachmentCount(), CometChat.MediaUploadListener. Correctly does not invent a public getMaxAttachmentSize() (size lives only in the internal getUploadLimits() helper). ✓
• Signatures & shapes match: callback signatures, { batchId, fileIds } return, "<batchId>:<index>" fileId format, rejected-vs-failed semantics, UploadResult shape.
• Constants match code: 30s stall timeout, 15-min presign TTL, ~1% progress throttle, 100 MB default size, 10 default count, and all 7 error codes match CometChatErrorConstants.ts exactly.
• All anchors resolve: #media-message, #multiple-attachments-in-a-media-message, #media-upload-errors, and the three /sdk/reference/* anchors.
• Nice cleanup: the stale "Starting version 3.0.9 & above" claim in send-message.mdx was removed.

🔹 Minor / optional (non-blocking)

• Verify with SDK author (likely a code quirk, not a doc issue): error-codes.mdx / upload-files.mdx present ERR_S3_UPLOAD_FAILED as unconditionally onFileFailure / retryable. That holds for the transport, abort, and whole-presign-failure paths, but in one path (UploadManager.processBatch → per-file presign entry with no form) the code calls rejectFile(…S3_UPLOAD_FAILED), surfacing it via onFileError (non-retryable). The blanket "retryable: Yes" is ~95% accurate.
• Pre-existing, out of scope: the link scanner flagged /sdk/javascript/{default-call, direct-call, standalone-calling, interactive-messages} as broken, but these live in unchanged files (all-real-time-listeners.mdx, message-structure-and-hierarchy.mdx) and one pre-existing link in send-message.mdx — not introduced by this PR. Noting only for visibility.

_{🤖 Automated docs review (Claude Code), cross-checked against the implementing code PR.}