docs: introduce Microsoft.UI.Reactor on first prose reference (#378)

Apply the naming convention that the first prose mention of "Reactor" in
each document is the fully qualified "Microsoft.UI.Reactor" (with an
optional "(Reactor)" parenthetical where the parenthetical reads well);
subsequent references stay as "Reactor". H1 headings, code identifiers
(ReactorApp, ReactorHost, ReactorD3, Reactor.SelfTests, etc.), YAML
frontmatter, and code fences are left untouched.

Scope (one edit per file):
- 61 guide templates under docs/_pipeline/templates/ (sources for
  docs/guide; regenerated via mur docs compile --no-screenshots)
- 79 spec docs under docs/specs/
- 16 reference/research/security/perf/aot docs
- 4 sample READMEs
- 1 pipeline meta (docs/_pipeline/ai-author-skill.md)
- 61 regenerated docs/guide/*.md outputs

Out of scope: docs/guide (generated; regenerated here), C# XML doc
comments, sample/src CHANGELOG entries, scaffold templates with no
prose Reactor.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: codemonkeychris

docs/_pipeline/ai-author-skill.md

@@ -12,7 +12,7 @@ goal: |
 tier: comprehensive
 ---
 
-Reactor's accessibility surface is two layers: modifiers that map to
+Microsoft.UI.Reactor (Reactor)'s accessibility surface is two layers: modifiers that map to
 WinUI automation properties (`.AutomationName`, `.HeadingLevel`,
 `.Landmark`, `.LiveRegion`, `.TabIndex`, `.AccessKey`) and hooks that
 add runtime behavior (`UseFocusTrap` for modal focus trapping,

docs/_pipeline/templates/accessibility.md.dt

@@ -13,7 +13,7 @@ goal: |
 tier: comprehensive
 ---
 
-Advanced is the layer where Reactor's declarative ceiling meets the
+Advanced is the layer where Microsoft.UI.Reactor (Reactor)'s declarative ceiling meets the
 imperative WinUI runtime underneath. Most of the framework is shaped to
 make the declarative path the right path — render is a function of
 state, the reconciler turns the next element record into a control

docs/_pipeline/templates/advanced.md.dt

@@ -14,7 +14,7 @@ goal: |
 tier: comprehensive
 ---
 
-Reactor ships a small Roslyn analyzer suite that catches mistakes the
+Microsoft.UI.Reactor (Reactor) ships a small Roslyn analyzer suite that catches mistakes the
 type system can't — conditional hook calls, missing list keys,
 hardcoded colors, icon buttons with no accessible name, stale closure
 captures in `UseMemoCells`, and missing XML docs on public API. The

docs/_pipeline/templates/analyzer-architecture.md.dt

@@ -14,7 +14,7 @@ goal: |
 tier: comprehensive
 ---
 
-Reactor's animation surface looks deceptively simple — set
+Microsoft.UI.Reactor (Reactor)'s animation surface looks deceptively simple — set
 `.Opacity(visible ? 1 : 0)` and attach `.OpacityTransition()`, and the
 property change animates on next render. Underneath, four distinct
 systems route into the same compositor layer: declaration-site implicit

docs/_pipeline/templates/animation-pipeline.md.dt

@@ -13,7 +13,7 @@ tier: comprehensive
 winui-ref: https://learn.microsoft.com/en-us/windows/apps/design/motion/
 ---
 
-Reactor exposes four animation systems and one rule about which to pick.
+Microsoft.UI.Reactor (Reactor) exposes four animation systems and one rule about which to pick.
 The rule first: the **compositor** can only animate five properties —
 Opacity, Offset (Translation), Scale, Rotation, and CenterPoint — and
 when it does, the managed render thread is not involved and the

docs/_pipeline/templates/animation.md.dt

@@ -14,7 +14,7 @@ goal: |
 tier: comprehensive
 ---
 
-Reactor is a declarative shell over WinUI. You write a `Component` whose
+Microsoft.UI.Reactor (Reactor) is a declarative shell over WinUI. You write a `Component` whose
 `Render()` method returns an immutable tree of element records — value
 types that describe what you want on screen, not the WinUI controls that
 implement it. A single reconciler diffs the new tree against the previous

docs/_pipeline/templates/architecture-overview.md.dt

@@ -14,7 +14,7 @@ tier: solid
 
 # Async Resources
 
-Reactor's async hooks — `UseResource`, `UseInfiniteResource`, and
+Microsoft.UI.Reactor (Reactor)'s async hooks — `UseResource`, `UseInfiniteResource`, and
 `UseMutation` — replace the "one `UseState` for data, one for loading, one
 for error, one `UseEffect` to tie them together" pattern. They own the
 fetch lifecycle: cancellation on deps-change, drop late results after

docs/_pipeline/templates/async-resources.md.dt

@@ -30,7 +30,7 @@ drop into D3 only when the higher-level surface refuses what you need.
 
 # Charting
 
-ReactorD3 brings data visualization to Reactor. The chart DSL provides high-level
+ReactorD3 brings data visualization to Microsoft.UI.Reactor (Reactor). The chart DSL provides high-level
 `LineChart`, `BarChart`, `AreaChart`, and `PieChart` factories that produce
 standard Reactor elements. You bind data, configure appearance with a fluent
 API, and the chart renders as native WinUI shapes on a Canvas.

docs/_pipeline/templates/charting.md.dt

@@ -13,7 +13,7 @@ tier: solid
 
 # Cheat Sheet
 
-Reactor at a glance. Every row links to the page that covers it in
+Microsoft.UI.Reactor (Reactor) at a glance. Every row links to the page that covers it in
 depth.
 
 ## Minimum viable app