CmdPal: Enhance font icon classification and visuals (#41573)

## Summary of the Pull Request

- Introduces `FontIconGlyphClassifier` for classifying emojis and
symbols.
- Correctly recognizes multi-codepoint glyphs (e.g., 🧙🏼‍♀️ *woman mage
with medium-light skin tone*).
- Explicitly disallows multi-glyph icons (they would overflow anyway).
- Distinguishes between emojis and regular text characters (letters,
numbers, symbols), since emojis are slightly larger and require
different padding.
- Recognizes Unicode [Variation
Selectors](https://en.wikipedia.org/wiki/Variation_Selectors_(Unicode_block))
to enforce specific styles: VS15 (U+FE0E) for text style (monochrome)
and VS16 (U+FE0F) for emoji style (color). This lets developers choose
which variant to display. By default, characters with both
representations render as text/monochrome (e.g., ▶ `\u25B6`):
<img width="428" height="39" alt="image"
src="https://github.com/user-attachments/assets/c5e6865f-61de-4f45-9f3a-4e15e5e5ceb8"
/>
- Invalid icons are displayed as a dashed circle so extension developers
can spot issues, without being overly distracting if they slip into
production.

- Updates `IconPathConverter` to use the new classifier for improved
icon handling.
- Adds `SampleIconPage` to demonstrate various icon usages and
classifications.
- Adjusts icon alignment in `IconBox` so icons are centered.  
- Scales negative padding for emojis in `IconBox` with control size,
fixing misalignment and clipping (noticeable in tags and the details
pane hero image).
- Applies negative padding to all font icons. This removes the need for
classification in these cases and ensures symbols rendered below the
baseline remain visible.

Based on
[microsoft/terminal#19143](https://github.com/microsoft/terminal/pull/19143):
Co-authored-by: Dustin L. Howett <duhowett@microsoft.com>

Pictures? Pictures!

<img width="1912" height="2394" alt="image"
src="https://github.com/user-attachments/assets/05a16309-b658-4f21-8f9d-9a3f20db6ad8"
/>

Keyboard and flag/country emojis may look a bit off, but that’s how
they’re actually rendered:
<img width="482" height="95" alt="image"
src="https://github.com/user-attachments/assets/dc7d4d0d-3dc8-4df5-9b9f-9e977e7e989f"
/>


<!-- Please review the items on the PR checklist before submitting-->
## PR Checklist

- [x] Closes: 
  - #41489 
  - #41496 
- [ ] **Communication:** I've discussed this with core contributors
already. If the work hasn't been agreed, this work might be rejected
- [ ] **Tests:** Added/updated and all pass
- [ ] **Localization:** All end-user-facing strings can be localized
- [ ] **Dev docs:** Added/updated
- [ ] **New binaries:** Added on the required places
- [ ] [JSON for
signing](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ESRPSigning_core.json)
for new binaries
- [ ] [WXS for
installer](https://github.com/microsoft/PowerToys/blob/main/installer/PowerToysSetup/Product.wxs)
for new binaries and localization folder
- [ ] [YML for CI
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/ci/templates/build-powertoys-steps.yml)
for new test projects
- [ ] [YML for signed
pipeline](https://github.com/microsoft/PowerToys/blob/main/.pipelines/release.yml)
- [ ] **Documentation updated:** If checked, please file a pull request
on [our docs
repo](https://github.com/MicrosoftDocs/windows-uwp/tree/docs/hub/powertoys)
and link it here: #xxx

<!-- Provide a more detailed description of the PR, other things fixed,
or any additional comments/features here -->
## Detailed Description of the Pull Request / Additional comments

<!-- Describe how you validated the behavior. Add automated tests
wherever possible, but list manual validation steps taken as well -->
## Validation Steps Performed

.github/actions/spell-check/expect.txt

@@ -306,6 +306,7 @@ CXVIRTUALSCREEN
 CYSCREEN
 CYSMICON
 CYVIRTUALSCREEN
+Czechia
 cziplib
 Dac
 dacl
@@ -436,6 +437,7 @@ EDITSHORTCUTS
 EDITTEXT
 EFile
 ekus
+emojis
 ENABLEDELAYEDEXPANSION
 ENABLEDPOPUP
 ENABLETAB
@@ -800,6 +802,7 @@ KEYBOARDMANAGEREDITORLIBRARYWRAPPER
 keyboardmanagerstate
 keyboardmanagerui
 keyboardtester
+keycap
 KEYEVENTF
 KEYIMAGE
 keynum
@@ -1781,10 +1784,13 @@ UACUI
 UAL
 uap
 UBR
+UBreak
+ubrk
 UCallback
 ucrt
 ucrtd
 uefi
+UError
 uesc
 UFlags
 UHash
@@ -1854,6 +1860,7 @@ VFT
 vget
 vgetq
 viewmodels
+virama
 VIRTKEY
 VIRTUALDESK
 VISEGRADRELAY