feat(integrations): save MCP tokens as secrets

[jpelletier1]

• A human has tested these changes.

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Why

Direct token-auth MCP connections should offer the same secret-saving behavior already available for GitHub and password-based transport fields.

Summary

• Add secret names and default secret-saving metadata for Linear, Ordinal, PostHog, and Stripe MCP tokens.
• Add regression coverage requiring direct MCP token credentials to support secret saving.

Issue Number

N/A

How to Test

npm run build:integrations
uv run pytest -q tests/test_catalogs.py tests/test_catalog_schema.py tests/test_integration_catalog_in_sync.py
uv run python scripts/sync_extensions.py --check

Expected result: the integration build succeeds, all tests pass, and the sync check exits successfully.

Video/Screenshots

Not applicable - catalog metadata and test-only changes.

Notes

Validation completed locally with 111 relevant tests passing. The sync check emitted one unrelated warning that plugins/issue-duplicate-checker is not listed in a marketplace.

This pull request was created by an AI agent (OpenHands) on behalf of the user.

@jpelletier1 can click here to continue refining the PR