Integrate Pipelines-as-Code documentation into tekton.dev

Summary

Now that Pipelines-as-Code (PAC) has joined the Tekton organization, its documentation should be integrated into tekton.dev alongside the other Tekton components (Pipelines, Triggers, CLI, Dashboard, Chains, etc.) rather than living on a separate standalone site (pipelinesascode.com).

Current State

• PAC docs are hosted separately using Hugo + Hextra theme at pipelinesascode.com
• tekton.dev has only a stub page under Getting Started that links out to pipelinesascode.com
• All other Tekton components (Pipelines, Triggers, CLI, Dashboard, Chains, Operator, Results) have their docs synced into tekton.dev via sync/sync.py with per-component YAML configs in sync/config/

Challenges

PAC's documentation structure is significantly different from the other Tekton components:

1. Different doc structure: Other components keep docs as flat markdown files in a docs/ folder in their repo. PAC uses a full Hugo site with nested content tree (docs/content/docs/) organized into sections: installation, guides, providers, operations, CLI, API, advanced, and dev.

2. Nested hierarchy: PAC docs have deep nesting (e.g., guides/creating-pipelines/, guides/event-matching/, guides/gitops-commands/, guides/llm-analysis/) that doesn't map cleanly to the current sync script's flat folder model.

3. Different theme/tooling: PAC uses the Hextra theme while tekton.dev uses Docsy. Front matter, shortcodes, and layout assumptions may differ.

Possible Approaches

1. Sync config approach: Create a sync/config/pipelines-as-code.yaml and extend sync.py to handle PAC's nested doc structure, mapping it into the tekton.dev content tree under content/en/docs/Pipelines-as-Code/.

2. Restructure PAC docs: Flatten or reorganize PAC's docs/ folder to match the pattern used by other Tekton components, then use the standard sync mechanism.

3. Hugo module / submodule approach: Mount PAC's docs content as a Hugo module directly into the website, preserving the hierarchy as-is.

4. Manual initial sync + sync script maintenance: Do a one-time import of PAC docs into the website repo, then maintain them there (similar to how some projects handle large doc sets).

Acceptance Criteria

• PAC documentation is accessible at tekton.dev/docs/pipelines-as-code/ (or similar path)
• Docs are versioned alongside PAC releases
• Navigation integrates cleanly with the existing tekton.dev sidebar
• The existing stub Getting Started page is updated to link to the integrated docs
• pipelinesascode.com redirects or links to tekton.dev for docs (eventual)

Start by reading sync/sync.py and the per-component configs in sync/config/, then compare their flat-document assumptions with PAC's nested docs/content/docs/ Hugo tree and the existing Getting Started stub. Identify the integration approach and any required navigation or front-matter handling. Done means PAC docs are available under tekton.dev, versioned with PAC releases, linked from the sidebar and stub, with the external site redirect or link addressed.