Initialize PSMA: one library-backed action dispatched by Mode

[Marius Storhaug (MariusStorhaug)]

Initialize PSMA — one library-backed action, dispatched by Mode

This lays the foundation for consolidating the framework's internal actions into a
single repository with a single lifecycle. It introduces one internal PowerShell
library that holds all framework action logic and one composite action whose
control script (main.ps1) loads the library and dispatches on a Mode input.

It replaces the fleet of one-capability action repositories (Build-PSModule,
Test-PSModule, Publish-PSModule, Resolve-PSModuleVersion,
Get-PSModuleSettings, Document-PSModule, Get-PesterCodeCoverage,
Get-PesterTestResults, Install-PSModuleHelpers) with one place to version, test,
and release them together.

Design

action.yml            single composite action; input `Mode` + parameters
└─ src/main.ps1       control script: imports the library, switches on Mode
   └─ src/PSMA/       the single internal library, reused by every mode
      ├─ functions/public/    one function per mode + the Initialize bootstrap
      └─ functions/private/   shared helpers reused across all modes

• The library is imported once and reused across every call, so version/build/test/
  publish logic lives in one module instead of being duplicated per action.
• Shared helpers (Write-PSMALog, Get-PSMAInput, Set-PSMAOutput,
  Get-PSMAModuleName) are defined once and used by every mode — this is what
  simplifies the individual action calls.
• Initialize-PSMA is the shared bootstrap that replaces the
  Install-PSModuleHelpers action.

Modes

Mode	Library function	Ports logic from
Settings	Get-PSMASettings	Get-PSModuleSettings
Version	Resolve-PSMAVersion	Resolve-PSModuleVersion
Build	Build-PSMAModule	Build-PSModule
Test	Test-PSMAModule	Test-PSModule
CodeCoverage	Get-PSMACodeCoverage	Get-PesterCodeCoverage
TestResults	Get-PSMATestResult	Get-PesterTestResults
Document	Build-PSMADocumentation	Document-PSModule
Publish	Publish-PSMAModule	Publish-PSModule

Testability

Because the action and the library live in one repo, CI tests both at the branch:

• Test-Module — Pester tests the library (module surface, shared helpers, Build mode).
• Action-Test — runs the action (uses: ./) for Settings, Version, and Build
  and asserts the outputs and the built manifest.
• Lint — PSScriptAnalyzer at error severity.

Consumers

A caller picks the task with Mode, otherwise nothing about how they invoke it changes:

- uses: PSModule/PSMA@<sha> # vX.Y.Z
  with:
    Mode: Build
    Name: MyModule
    Version: 1.2.3

Not yet (follow-up)

Each mode function is a working skeleton with a PORT FROM: marker; the real logic
from each existing action is moved in as a follow-up (one PR per capability), the
generic actions (GitHub-Script, Invoke-Pester, Invoke-ScriptAnalyzer) stay
standalone, and the reusable workflows are re-pointed at PSMA last.