[Index / structure] bridgelet-audit/runbooks/README.md: Runbooks subfolder index

[phertyameen]

Index / structure: bridgelet-audit/runbooks/README.md

Purpose:
Create an index file listing every runbook with a one-line 'when to use this' summary and link.

This file should cover:

• Group entries by whether they're routine operations, incident-response, or pre-flight/validation procedures.
• Note that runbooks describe current behavior and operational workarounds, not proposed code changes.
• Keep the index scannable for someone in the middle of an incident who needs to find the right runbook fast.

Scope: documentation-only addition to a new, standalone folder. No changes to contracts/, docs/, scripts/, or tools/ are needed to close this issue.

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Part of the bridgelet-audit/ knowledge-base initiative (97/100).

[Peolite001]

i would love to work on this issue

[grantfox-oss]

🦊 GrantFox — @Peolite001 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #348)
2. Your PR will be reviewed by the bridgelet-org maintainers

Good luck! Track your progress on GrantFox.