Generate PowerShell docs from code - #935

…nd reference docs

Adds src/scripts/Build-Documentation.ps1, which regenerates the MS Learn
PowerShell command reference pages under docs-mslearn/toolkit/powershell/
from each command's comment-based help (based on the parsing approach from
the never-merged PR #935, retargeted to the current MS Learn template
instead of the old Jekyll docs/_automation format).

Ports forward the comment-based help improvements from PR #935 where dev's
current help didn't already cover them, and fixes several pre-existing doc
bugs surfaced by generation: wrong/stale parameter names (DataSet vs
Dataset, -ResourceGroup vs -ResourceGroupName), the "how to use the what
{Command}" customer-intent typo, single-quoted vs backtick-wrapped
parameter names, a wrong command name in a customer-intent comment, a
copy-pasted example title, a stale RunHistory return-value shape, and
several commands (Deploy-FinOpsHub, New-FinOpsCostExport) whose docs were
missing parameters added to source since the doc was last hand-written.
Adds the previously-undocumented Add-FinOpsHubScope command's reference
page and lists it (plus other previously-missing commands) in the index
pages.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>