Run the documentation pipeline when doc/ is edited + various rendering fixes

[OneBlue]

Summary of the Pull Request

This change adds logic to run the documentation pipeline on pull request (building, not deploying), and solves various markdown issues (which will also allow deployment testing once merged)

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Pull request overview

This PR updates the GitHub Pages documentation workflow so documentation builds run on pull requests that touch doc/**, while deployments remain push-only. It also applies a set of Markdown formatting fixes across the docs to improve list/section rendering and correct an invalid C++ snippet initialization.

Changes:

• Add a pull_request trigger to the documentation workflow and split build vs. deploy into separate jobs (deploy gated to push only).
• Adjust workflow concurrency grouping to be per-ref to avoid unrelated runs cancelling each other.
• Fix Markdown rendering issues by inserting blank lines before lists/sections and correct = ; placeholders to {} in a C++ example.

Reviewed changes

Copilot reviewed 40 out of 40 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
doc/docs/debugging.md	Adds spacing to ensure Markdown list renders correctly after the code block.
doc/docs/api-reference/csharp/settings-classes/vhdoptions.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/csharp/settings-classes/sessionsettings.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/csharp/settings-classes/processsettings.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/csharp/settings-classes/containersettings.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/csharp/data-classes/containerportmapping.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/csharp/core-classes/process.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/csharp/core-classes/container.md	Inserts blank line after “Notes:” to improve list rendering.
doc/docs/api-reference/cpp/settings-classes/vhdoptions.md	Adds spacing before properties list for consistent Markdown rendering.
doc/docs/api-reference/cpp/settings-classes/sessionsettings.md	Adds spacing before constructor/properties sections for consistent rendering.
doc/docs/api-reference/cpp/settings-classes/processsettings.md	Adds spacing before properties/notes sections for consistent rendering.
doc/docs/api-reference/cpp/settings-classes/containersettings.md	Adds spacing before constructor/properties/notes sections for consistent rendering.
doc/docs/api-reference/cpp/service-class/wslcservice.md	Adds spacing before methods/behavior notes lists for consistent rendering.
doc/docs/api-reference/cpp/enumerations/vhdtype.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/signal.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/sessionterminationreason.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/processstate.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/processoutputmode.md	Adds spacing before underlying values/behavior lists for consistent rendering.
doc/docs/api-reference/cpp/enumerations/processoutputhandle.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/portprotocol.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/imageprogressstatus.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/error.md	Adds spacing before underlying HRESULT list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/deletecontaineroption.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/containerstate.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/enumerations/containernetworkingmode.md	Adds spacing around validation/underlying values lists for consistent rendering.
doc/docs/api-reference/cpp/enumerations/component.md	Adds spacing before underlying values list for consistent rendering.
doc/docs/api-reference/cpp/delegates-and-events/sessionterminationhandler.md	Adds spacing before observed-use list for consistent rendering.
doc/docs/api-reference/cpp/delegates-and-events/processoutputhandler.md	Adds spacing before observed-use list for consistent rendering.
doc/docs/api-reference/cpp/delegates-and-events/processexithandler.md	Adds spacing before observed-use list for consistent rendering.
doc/docs/api-reference/cpp/delegates-and-events/processcrashhandler.md	Adds spacing before observed-use list for consistent rendering.
doc/docs/api-reference/cpp/data-classes/installprogress.md	Adds spacing before properties list for consistent rendering.
doc/docs/api-reference/cpp/data-classes/imageprogress.md	Adds spacing before properties list for consistent rendering.
doc/docs/api-reference/cpp/data-classes/imageinfo.md	Adds spacing before properties list for consistent rendering.
doc/docs/api-reference/cpp/data-classes/containervolume.md	Adds spacing before constructors/properties list for consistent rendering.
doc/docs/api-reference/cpp/data-classes/containerportmapping.md	Adds spacing before constructors/properties and notes lists for consistent rendering.
doc/docs/api-reference/cpp/data-classes/containernamedvolume.md	Adds spacing before constructors/properties list for consistent rendering.
doc/docs/api-reference/cpp/core-classes/session.md	Adds spacing between sections and fixes invalid C++ example initializations to {}.
doc/docs/api-reference/cpp/core-classes/process.md	Adds spacing before method/notes lists for consistent rendering.
doc/docs/api-reference/cpp/core-classes/container.md	Adds spacing before method/notes lists for consistent rendering.
.github/workflows/documentation.yml	Runs doc build on PRs touching doc/** and gates deploy to push-only via separate jobs.