Move signature help and hover tests to the end-to-end tier

[Firehed]

Summary

Stacked on #685.

Moves the signature help and hover suites onto the end-to-end tier.

Request steps

• Hover checks Shows(...) and Hides(...), fragments of the content, Formatted(MarkupKind), and NoAnswer(). HoverContent decodes the MarkupContent form this server sends.
• SignatureHelp checks the active signature: SignatureShows(...) and DocumentationShows(...), fragments of the label and documentation, and ActiveParameter(index); plus SignatureCount(n) and NoAnswer() on the whole answer. SignatureHelpResult decodes the answer with the protocol's defaults for the active signature and parameter.

Scripts

• One script per case of both suites, opening the same files the originals opened. Each expectation is one of the original's assertions.
• Built-in cases are scripts too: array_map signature help, and hover on sort, ArrayObject::getArrayCopy, Exception::$message, and DateTime::getTimestamp through clone and ??. Their full answers were identical on PHP 8.4, 8.5, and 8.6 in CI. The README now allows a built-in in a script when its output is the same on every version in the matrix, instead of keeping built-ins out.
• ClientCapabilities can declare markdown hover support (textDocument.hover.contentFormat). One script in transcripts/ expects a markdown answer and locks its fenced format. Nothing exercised markdown hover before.
• The inline "hover inside a comment" case uses a new fixture, EdgeCases/HoverInComment.php.

Unit tests

ExpressionResolutionTest covers the paths only the hover suite reached:

• a foreach element type taken from a @return User[] docblock: through a use import, fully qualified, naming no known class, and with no element type;
• clone keeping the copied type;
• ?? resolving through its left side.

The tests stub the symbol source and type source with only what each case needs.

Originals

HoverHandlerIntegrationTest and SignatureHelpHandlerIntegrationTest are removed.

Coverage: unchanged, file by file.

Noted, not changed

A single-line docblock (/** Text. */) reaches hover and signature help documentation with its closing */, for example "Static method documentation. */". The expectations check fragments, so they hold whether or not this is fixed. Tracked in #689.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.67%. Comparing base (636ff05) to head (9ea8e79).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@                 Coverage Diff                 @@
##             e2e-disk-changes     #686   +/-   ##
===================================================
  Coverage               99.67%   99.67%           
  Complexity               1900     1900           
===================================================
  Files                     135      135           
  Lines                    4873     4873           
===================================================
  Hits                     4857     4857           
  Misses                     16       16           

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