docs: document getSecureCredentials error code 21

[riderx]

What

• Document error code 21 (NO_PROTECTED_CREDENTIALS_FOUND) for getSecureCredentials() when no biometric-protected credentials exist for the requested server
• Add BiometricAuthError.NO_PROTECTED_CREDENTIALS_FOUND to the TypeScript enum so consumers can reference the code in app logic
• Expand README Biometric Auth Errors table and getSecureCredentials() API docs with platform-specific rejection messages

Fixes #108

Why

• Callers of getSecureCredentials() can receive rejection code 21 when credentials were never stored with biometric protection, were deleted, or were invalidated (for example after biometric enrollment changes)
• This behavior is stable and expected, but was undocumented — making it hard for TypeScript consumers to handle intentionally

How

• Added code 21 to the manual README error table with Android/iOS message differences:
  • Android: No protected credentials found
  • iOS: No protected credentials found for server
• Added NO_PROTECTED_CREDENTIALS_FOUND = 21 to BiometricAuthError in src/definitions.ts
• Documented the rejection in getSecureCredentials() JSDoc and regenerated API docs via bun run docgen

Testing

• bun run build
• bun run lint

Not Tested

• No runtime changes; native behavior unchanged. No new unit tests added (repo does not currently test plugin error codes this way).

  

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Summary by CodeRabbit

• New Features

  • Added a biometric authentication error for cases where no protected credentials or data are available.
  • Added platform-specific error messaging and guidance for handling missing secure credentials.
  • Clarified that secure credential retrieval rejects with the new error when no protected data exists.
  • Added the new error code to the public biometric authentication error reference.

• Documentation

  • Expanded authentication and secure credential retrieval documentation, including behavior and secure recovery guidance.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: ASSERTIVE

Plan: Pro

Run ID: 4829045e-5c71-49b0-8007-216ba5876e64

📥 Commits

Reviewing files that changed from the base of the PR and between 5c285fc and 97e002c.

📒 Files selected for processing (2)

• README.md
• src/definitions.ts

🔗 Linked repositories identified

CodeRabbit considers these linked repositories for cross-repo context during reviews:

• Cap-go/capacitor-updater (manual)

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📝 Walkthrough

Walkthrough

The plugin now documents biometric error code 21 for missing protected credentials or data. The public error enum includes NO_PROTECTED_CREDENTIALS_FOUND = 21, with platform-specific messages and guidance for getSecureCredentials() handling.

Changes

Secure retrieval error contract

Layer / File(s)	Summary
Error contract src/definitions.ts	Added NO_PROTECTED_CREDENTIALS_FOUND = 21 and documented its rejection payloads, triggering conditions, platform messages, and availability.
Secure retrieval documentation README.md, src/definitions.ts	Documented error code 21 for getSecureCredentials() and getSecureData(), including storage scenarios and isCredentialsSaved() limitations.

Estimated code review effort: 1 (Trivial) | ~5 minutes

Mergeability Score: ⚪ Minimal · up to 97e00

This localized documentation and enum update does not introduce an actionable merge-blocking risk; it is merge-ready after normal checks and review.

Possibly related PRs

• Cap-go/capacitor-native-biometric#86: The change extends the secure credential retrieval flow documented by PR #86.

Suggested reviewers: cursoragent

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the primary change: documenting error code 21 for getSecureCredentials.
Linked Issues check	✅ Passed	The changes document error code 21, its iOS and Android messages, triggering scenarios, and getSecureCredentials behavior as requested in issue #108.
Out of Scope Changes check	✅ Passed	The README and enum updates directly support issue #108, and no unrelated runtime changes are present.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

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[cubic-dev-ai]

All reported issues were addressed across 2 files

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