feat(web): add percentage bar annotation renderer

[warun7]

Summary

Adds the percentageBar annotation renderer to supervision-js, providing proportional progress and confidence bar indicators anchored to detection bounding boxes.

Closes #103

Motivation & Use Cases

• Visualize model confidence scores, tracking probabilities, or custom progression values directly on detections.
• Supports flexible placement (Top, Bottom, InsideTop, InsideBottom), custom heights, border styling, padding, and dynamic fill opacity.
• Preserves the session-first presentation model where renderers remain presentation-only and decoupled from core detection semantics.

Visual Demo

Changes

1. Core Styles & Contracts (@supervision/core)

• Added PercentageBarStyle, PercentageBarPlacement, and PercentageBarDrawInstruction interfaces in packages/core/src/types/percentage-bar-style.ts.
• Implemented BasePercentageBarStyle with value clamping in [0, 1], geometric alignment based on placement, and configurable color/stroke options in packages/core/src/styles/percentage-bar-style.ts.
• Added annotationRenderers.percentageBar factory and integrated it into default presentation and source presentation registries.

2. Vector Layer Scene Lowering (@supervision/web)

• Updated annotation-shape-styles.ts to lower PercentageBarDrawInstruction into closed rectangular polygon paths for background track and value progress.
• Made stroke optional on ClosedPathShapeInstruction in packages/core/src/types/shape-style.ts and guarded vector layer stroke rendering in pixi-vector-layer.ts.
• Wired percentageBarStyle through MediaRendererPresentation, pixi-media-scene.ts, and media-renderer-core.ts.

3. Documentation & Playground (demo, docs, tools)

• Added dedicated guide and live interactive playground in docs/public/annotation-renderers/percentage-bar.md.
• Added "percentage-bar" playground controls (Height slider, Fill Opacity slider, Placement select) in demo/src/docs-annotation-renderer.ts.
• Updated TypeDoc public API facade and test contracts in tools/docs-contract.test.mjs and tools/package-smoke.test.mjs.

Validation

• npm run verify passed cleanly:
  • prettier --check passed.
  • eslint passed with 0 errors / 0 warnings.
  • tsc passed across all workspace packages and demo.
  • vitest run passed all 843 tests across 103 test suites.
  • package-boundary.test.mjs passed (7/7).
  • docs-contract.test.mjs passed (14/14).
  • package-smoke.test.mjs passed runtime and typing export assertions.
• npm run package:tarball && npm run package:tarball:smoke passed (8/8).

[joaomarcoscrs]

I found two issues in the initialization and drawing paths.