fix(#582): redact sensitive webhook headers from error logs

[OneStepAt4time]

Summary

Redacts sensitive header values (Authorization, Cookie, X-API-Key, etc.) from webhook error logs to prevent secret leakage.

Changes

• src/utils/redact-headers.ts (new) — redactHeaders() and redactSecretsFromText() utilities
• src/channels/webhook.ts — applies header redaction in error catch blocks
• src/__tests__/webhook-header-redaction.test.ts — 113 lines of tests covering all sensitive patterns

Scope

Minimal: 3 files, +170 -1 lines. No unrelated changes.

Fixes #582

Quality Gate

• tsc --noEmit — zero errors
• npm run build — success
• npm test — 77 files, 1776 tests passed

[gitguardian]

⚠️ GitGuardian has uncovered 1 secret following the scan of your pull request.

Please consider investigating the findings and remediating the incidents. Failure to do so may lead to compromising the associated services or software components.

🔎 Detected hardcoded secret in your pull request

GitGuardian id	GitGuardian status	Secret	Commit	Filename
29378933	Triggered	X-API-Key Secret	78be71c	src/tests/webhook-header-redaction.test.ts	View secret

🛠 Guidelines to remediate hardcoded secrets

1. Understand the implications of revoking this secret by investigating where it is used in your code.
2. Replace and store your secret safely. Learn here the best practices.
3. Revoke and rotate this secret.
4. If possible, rewrite git history. Rewriting git history is not a trivial act. You might completely break other contributing developers' workflow and you risk accidentally deleting legitimate data.

To avoid such incidents in the future consider

• following these best practices for managing and storing secrets including API keys and other credentials
• install secret detection on pre-commit to catch secret before it leaves your machine and ease remediation.

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^{🦉 GitGuardian detects secrets in your source code to help developers and security teams secure the modern development process. You are seeing this because you or someone else with access to this repository has authorized GitGuardian to scan your pull request.}

[OneStepAt4time]

🚨 Bug audit verified: STILL PRESENT

webhook.ts:119-127 still leaks session metadata (id, name, workDir) in payload. No redaction applied.

New tracking issue: #827 (P2)