fix(tooltip): avoid duplicate overlay semantics

[leoafarias]

Description

Excludes NakedTooltip visual overlays from semantics by default, keeping
semanticLabel on one interactive trigger node. Custom overlays can opt into
independent semantics with excludeOverlaySemantics: false; visual and
interaction behavior is unchanged.

Validation: fvm dart run melos ci and the focused tooltip semantics suite.

Related Issues

Related to #81. Found while validating conceptadev/remix#80.

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Checklist

• My PR includes unit or integration tests for all changed behavior.
• I have updated the API and widget documentation.
• I am prepared to follow up on review comments in a timely manner.

Breaking Change

• Yes, this is a breaking change.
• No, this is not a breaking change.

[github-actions]

LCOV of commit 99d55c2 during Flutter CI #269

	(use "lcov --ignore-errors deprecated,deprecated ..." to suppress this warning)
Reading tracefile /tmp/__zgosalvez_github-actions-report-lcov/lcov.info.
Summary coverage rate:
  source files: 22
  lines.......: 89.6% (2947 of 3289 lines)
  functions...: no data found
  branches....: no data found
Message summary:
  1 warning message:
    deprecated: 1

Files changed coverage rate:
  	(use "lcov --ignore-errors deprecated,deprecated ..." to suppress this warning)
                                                                   |Lines       |Functions  |Branches    
  Filename                                                         |Rate     Num|Rate    Num|Rate     Num
  packages/naked_ui/lib/src/naked_tooltip.dart                     |83.9%    199|    -     0|    -      0

[Copilot]

Pull request overview

This PR updates NakedTooltip semantics to prevent duplicate accessible announcements when the tooltip is open by excluding the overlay subtree from the semantics tree by default, keeping tooltip semantics on the trigger node.

Changes:

• Added excludeOverlaySemantics to control whether the overlay subtree participates in semantics.
• Wrapped the tooltip overlay builder output with ExcludeSemantics (when enabled) to avoid duplicate overlay labels.
• Expanded the tooltip semantics test suite and updated widget documentation to describe the new behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
packages/naked_ui/lib/src/naked_tooltip.dart	Adds excludeOverlaySemantics and applies ExcludeSemantics to overlay content.
packages/naked_ui/test/semantics/naked_tooltip_semantics_test.dart	Adds semantics traversal helpers and new tests asserting no duplicate labeled nodes by default, with an opt-in for custom overlay semantics.
docs/widget/tooltip.mdx	Documents the new parameter and the intended default semantics behavior.

Comments suppressed due to low confidence (1)

docs/widget/tooltip.mdx:110

• This behaviour note implies the overlay is always semantics-excluded by default, which can leave tooltips inaccessible if semanticLabel isn’t provided. If overlay semantics are only excluded when semanticLabel is present, clarify that here as well so readers know which node will be announced.

- Only one tooltip is shown at a time when using nested tooltips
- Visual overlay content is semantics-excluded by default; use `semanticLabel` to describe it on the trigger

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[github-actions]

LCOV of commit a38a6ff during Flutter CI #270

	(use "lcov --ignore-errors deprecated,deprecated ..." to suppress this warning)
Reading tracefile /tmp/__zgosalvez_github-actions-report-lcov/lcov.info.
Summary coverage rate:
  source files: 22
  lines.......: 89.6% (2949 of 3291 lines)
  functions...: no data found
  branches....: no data found
Message summary:
  1 warning message:
    deprecated: 1

Files changed coverage rate:
  	(use "lcov --ignore-errors deprecated,deprecated ..." to suppress this warning)
                                                                   |Lines       |Functions  |Branches    
  Filename                                                         |Rate     Num|Rate    Num|Rate     Num
  packages/naked_ui/lib/src/naked_tooltip.dart                     |84.1%    201|    -     0|    -      0