Close specification coverage gaps for actionpins/stats and sync README APIs for workflow/parser/cli

[Copilot]

The package specification audit reported two missing package READMEs and API drift in three existing package specs. This PR fills the missing specs and aligns exported API documentation with current code.

• Add missing package specifications

  • Added pkg/actionpins/README.md with package overview, public types/functions, dependencies, and thread-safety notes.
  • Added pkg/stats/README.md documenting StatVar behavior and all exported methods.

• Sync workflow engine docs with current API

  • Updated pkg/workflow/README.md to include Gemini in engine overview/registry.
  • Added GeminiEngine and NewGeminiEngine() to public API tables.

• Sync parser docs with newly exported helpers

  • Updated pkg/parser/README.md with the 9 missing exported functions from:
    • virtual_fs.go
    • tools_merger.go
    • workflow_update.go

• Sync CLI docs with exported action command functions

  • Updated pkg/cli/README.md to document:
    • ActionsBuildCommand
    • ActionsValidateCommand
    • ActionsCleanCommand
    • GenerateActionMetadataCommand

// Newly documented parser API examples
func RegisterBuiltinVirtualFile(path string, content []byte)
func MergeTools(base, additional map[string]any) (map[string]any, error)
func UpdateWorkflowFrontmatter(workflowPath string, updateFunc func(frontmatter map[string]any) error, verbose bool) error

[Copilot]

Pull request overview

Adds missing package specifications and synchronizes several package READMEs so their documented public APIs match the current exported Go code (per the spec audit).

Changes:

• Added missing package specs for pkg/actionpins and pkg/stats.
• Updated pkg/workflow docs to include the Gemini engine in the overview and public API tables.
• Updated pkg/parser and pkg/cli docs to include newly exported helper/command functions.

Show a summary per file

File	Description
pkg/workflow/README.md	Documents Gemini as a supported workflow engine and adds it to the engine API tables.
pkg/stats/README.md	New package spec documenting StatVar and its exported methods/behavior.
pkg/parser/README.md	Adds missing exported helper functions (virtual FS, tools merge, workflow frontmatter update) to the public API table.
pkg/cli/README.md	Documents exported action-related CLI command functions.
pkg/actionpins/README.md	New package spec documenting action pin resolution types/functions and thread-safety notes.

Copilot's findings

Tip

Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

• Files reviewed: 5/5 changed files
• Comments generated: 3