Add blog post: Keyless Security with Tekton Chains

[anithapriyanatarajan]

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Adds a new blog post: Keyless Security with Tekton Chains.

The post explains keyless signing with Tekton Chains in practical terms:

• What Tekton Chains is and what it signs
• The keyless / Sigstore identity-based model in a nutshell
• How keyless works inside Tekton including a Mermaid diagram of the full signing flow
• How to turn it on (config map snippets)
• Verifying signatures via Rekor
• The full menu of signing options (keyless, x509, cosign keypair, KMS)
• Caveats: OIDC token format, cluster OIDC prerequisite, public vs. private infra, and the need for verification/policy

File added: content/en/blog/2026/keyless-security-with-tekton-chains/index.md

[anithapriyanatarajan]

/kind documentation

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/cc @jkhelil @arewm

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[arewm]

I added some comments and included some from Claude as well.

One thing that I struggle with, especially with how this post ends, is how should consumers treat Chains signatures? Chains has no ability to gate its signing based on whether artifacts are good/bad... this results in similar confusion to recent attacks where compromised npm packages had valid SLSA provenance.

When talking about identities, attestations, and signatures, we need to make sure we don't overly-trust the identity/metadata. I view a signature as essentially an "empty" VSA ... but because it is empty, consumers have no ability to consume it to gate anything.

[anithapriyanatarajan]

/hold