feat(progress)!: port to pf-v6-progress element (#3152)

* feat(progress): port pf-v5-progress to pf-v6-progress

Update progress bar element for PatternFly v6 with inline SVG status
icons, InternalsController, `helper-text` `@slot`, `value-text` and
`static-width` properties, `singleline` measure location, and v6
design tokens with CSS grid layout.

Closes #3031

Assisted-By: Claude Opus 4.6 <noreply@anthropic.com>

* fix(progress): address review findings from a11y, API, and demo audits

Move progressbar role and all ARIA to host via InternalsController,
fix aria-valuemax to always be 100, remove unnecessary value reflection,
guard fade-in animation with prefers-reduced-motion, rename failure
demos to danger, and inline demo wrapper styles.

Assisted-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat(progress): port pf-v5-progress to pf-v6-progress

* fix(progress): singleline should be derived not an attribute

* fix(progress): correct missing hide-status-icon and correct info around toolip

* fix(progress): handle describedby like labelledby

* fix(progress): use @observes instead of willUpdate

* chore(progress): add changeset

* docs: readme, manifest

* fix: aria-describedby

---------

Co-authored-by: Benny Powers <web@bennypowers.com>

Author: zeroedin

.changeset/calm-friends-carry.md

@@ -0,0 +1,23 @@
+---
+"@patternfly/elements": major
+---
+
+`<pf-v6-progress>`: replaces `<pf-v5-progress>` with PatternFly v6 design specs.
+
+```html
+<pf-v6-progress value="33" description="Loading..."></pf-v6-progress>
+```
+
+**Breaking Changes from v5**
+
+- Renamed tag from `<pf-v5-progress>` to `<pf-v6-progress>`
+- CSS custom properties renamed from `--pf-v5-c-progress--*` to `--pf-v6-c-progress--*`
+
+**New features**
+
+- `accessible-label` attribute for screen reader text via ElementInternals
+- `value-text` attribute for custom `aria-valuetext` (finite step displays)
+- `truncated` attribute for ellipsis overflow on description
+- `hide-status-icon` attribute for tight layouts
+- `helper-text` slot for supplementary text below the bar, auto-wired to `aria-describedby`
+- v6 design tokens and `light-dark()` support