fix(publish): expose entry public paths to publish filters

[EuanTop]

Summary

• add the emitted public pathname to the publish.html runtime context and shared publish filter SDK context
• preserve slug as the rendered page or template document identity
• derive path from the same route URL used by live rendering, static baking, preview, and background republish
• document the filter-context semantics and add regression coverage

For entry routes, slug identifies the shared entry template while
path identifies the concrete public artifact, for example
/posts/hello-world.

This allows SEO plugins to generate per-entry canonical and Open Graph URLs
without changing the existing template identity semantics.

Closes #225.

Verification

• bun run build
• bun test
• bun run lint
• Docker/deployment check, if relevant (not applicable)

Checklist

• Tests cover behavior changes.
• Docs were updated when behavior, config, deployment, or public surfaces changed.
• No compatibility shim was added for old pre-release behavior.
• No secrets, local databases, uploads, or generated artifacts are included.

[Copilot]

Pull request overview

This PR extends the publish filter context so publish.html handlers can reliably access the public URL pathname (path) of the emitted page/artefact (especially important for entry/template routes where slug identifies the template document, not the per-entry public route).

Changes:

• Add path to the renderer output and thread it through the publish.html filter context (bake/live/preview/republish flows).
• Update plugin SDK types and documentation to define the slug vs path semantics for entry routes.
• Add regression coverage asserting path is present for both / and entry routes.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/core/plugins/hookBus.ts	Updates inline docs for filter context extras.
src/core/plugin-sdk/types/hooks.ts	Introduces a shared PublishFilterContext including path for publish filters.
src/tests/server/publicRendering.test.ts	Ensures hookBus state is reset per test; asserts publish filter context includes path for /.
src/tests/server/cmsTemplateRoutes.test.ts	Adds regression test that entry route renders provide path (and keep template slug).
src/tests/architecture/publish-html-filter-context.test.ts	Updates test description to reflect path being part of the expected context contract.
server/publish/republish.ts	Changes background republish to use a page permalink-derived synthetic URL.
server/publish/publishedHtmlPipeline.ts	Passes path into the publish.html filter context extras.
server/publish/publicRenderer.ts	Makes url mandatory in render contexts and reports path via url.pathname on renderer output.
server/plugins/protocol/messages.ts	Updates protocol docs for filter context fields.
server/handlers/cms/data/preview.ts	Adds path to preview renderer output fed into the shared publish pipeline.
docs/features/publisher.md	Documents publish.html filters receiving { siteId, pageId, slug, path }.
docs/features/plugin-system.md	Adds canonical URL example using path and documents slug vs path semantics.

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[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.

Comments suppressed due to low confidence (1)

src/tests/architecture/publish-html-filter-context.test.ts:7

• The header comment overstates what this architecture gate enforces. The test only checks that applyFilter('publish.html', ...) is called with a third argument, not that the context contains specific keys like path. Reword the comment to match the actual guarantee (presence of a context argument), while still noting that handlers commonly destructure { siteId, pageId, slug, path }.

 * This ensures that plugin filter handlers for `publish.html` always receive
 * `{ siteId, pageId, slug, path }` in their context — without this, plugins that
 * destructure those fields would silently receive `undefined`.

[Copilot]

Pull request overview

Copilot reviewed 15 out of 15 changed files in this pull request and generated no new comments.