feat(completion): array callable method completion

[calebdw]

Summary

Add method name completion inside array callable strings. When the cursor is inside the method-name string of [Class::class, '|'] or [$obj, '|'], the LSP now offers method completions from the resolved class.

Motivation

The array-callable navigation work (commit 21a0105) added go-to-definition, find-references, and rename for array callable method strings. This PR extends that with completion — the last missing piece for a full editing experience with array callables like Route::get('/', [IndexPageController::class, 'indexPage']).

What's included

Detection (detect_array_callable_context)

• Scans backward from cursor to identify [Class::class, '|'] and [$var, '|'] patterns
• Handles ::class constants, $this, typed variables, namespaced classes
• Whitespace-tolerant, works with unclosed strings (user still typing)
• Rejects non-identifier content (e.g. [$this, 'not a method'])

Completion (try_array_callable_completion)

• Resolves the class from the first array element:
  • Class::class → FQN resolution via use map / namespace / bare name
  • $this → enclosing class
  • Other variables → full variable type resolution
• Reuses build_union_completion_items from the standard member-completion builder, so items have identical formatting to regular -> / :: completions:
  • Label details with class name
  • Return type in detail
  • Deprecation tags
  • data field for lazy documentation resolve (completionItem/resolve)
• Post-processes to strip snippet parentheses from insert_text since we're inserting into a string literal
• Filters to methods only (no properties/constants)
• Shows both instance and static methods (PHP array callables work with either)
  • Note, this requires feat(completion): include static methods on instance access #163 to work properly

Integration

• Hooked into handle_completion before the InStringLiteral suppression, alongside array shape and Eloquent string completions
• Registered in completion/mod.rs with module docs

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 87.45387% with 34 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/completion/array_callable.rs	87.16%	34 Missing ⚠️

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