test: guard plugin csp-search agent/skill copies against template drift #124

Problem

plugins/csp/agents/csp-search.md and plugins/csp/skills/csp-search/SKILL.md are hand-synced copies of the csp init agent templates in crates/csp/src/bin/csp/agents/*.md. Only the embedded templates are covered by a unit test (agent_templates_match_cli_output_and_auto_cache in crates/csp/src/bin/csp/main.rs). If someone edits a template and forgets the plugin copies, nothing catches it. PR #122 had to update all of these files by hand.

Proposal

Add a guard that fails when the plugin copies drift from the templates. Two options:

• A Rust test that reads the plugin files (via CARGO_MANIFEST_DIR, skipped when the files are absent, so isolated crate builds such as crates.io packaging still pass) and runs the same assertions, or compares bodies after stripping frontmatter.
• A CI script that strips frontmatter and the skill-only header from each copy and diffs the bodies against an agent template.

Acceptance criteria

• A change to the shared template body that is not mirrored in both plugin copies fails CI.
• Isolated crate builds (cargo package / crates.io) are unaffected.

Out of scope

• The README / README.ko / docs/src/content/docs/agents-md.mdx snippet copies (those are prose docs, not shipped agent definitions).

Context

• Review thread: fix(init): align agent templates with csp output and auto-cache #122 (comment)
• PR: fix(init): align agent templates with csp output and auto-cache #122 (closes csp init / plugin agent templates: wrong filePath key, stale "index not auto-updated" guidance, missing --max-snippet-lines #111)