feat: validate and lower properties by language

[adamcavendish]

Summary

Add semantic property capability profiles and complete language-local property
lowering. Property declarations now validate before lowering, preserve
structured types and metadata, and fail closed when a target cannot represent
the requested behavior. A validation-only owner view also covers relationships
between properties and explicit members without introducing shared grammar.

Problem

PropertySpec previously selected a shared accessor-versus-field grammar and
assembled target syntax from general configuration hooks. That allowed
unsupported contexts and invalid language forms to reach plausible-looking
output, kept property preamble ownership in the generic spec layer, and left
target-derived cross-member name collisions unchecked.

Behavior

Situation	Behavior
JavaScript or TypeScript concrete property	Lower to native getter and setter declarations
Kotlin or Swift computed property	Lower with target-owned computed-property grammar
PHP or Scala property intent	Lower to target-local getter and setter methods
Exact duplicate property names	Return one crate-owned structured error
PHP accessor or explicit-method collision	Reject the case-insensitive target member-name collision
Unsupported context or semantic combination	Return a structured validation error before lowering
Property type or importable annotation	Preserve structured references through import and alias resolution
Pre-0.6.8 external adapter	Use the frozen compatibility lowerer and deprecated grammar hooks

Compatibility

PropertyStyle, CodeLang::property_style(), and
CodeLang::property_getter_keyword() remain available but are deprecated.
External adapters that rely on the 0.6.8 defaults retain frozen compatibility
lowering, including valid split-member placement and preamble behavior.
Built-in adapters use strict property profiles and complete local lowerers.
Invalid legacy output may now be rejected.

TypeMembersIntent is a validation-only view with no lowering counterpart.
It carries semantic fields, computed properties, and explicit methods for one
owner; it does not contain placement or target grammar.

Validation

• just check
• just coverage-nextest
• just book
• just book-test
• RUSTDOCFLAGS=-Dwarnings cargo doc --workspace --no-deps
• cargo semver-checks check-release --baseline-rev origin/main
• git diff --check

Normal nextest passed 2,341 tests. Coverage nextest passed 2,191 tests. The new
owner-wide validation modules have 100% line and function coverage. The semver
comparison against origin/main passed all 196 applicable checks.

[codecov]

Codecov Report

❌ Patch coverage is 97.26942% with 45 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/lang/capability.rs	81.33%	14 Missing ⚠️
src/error.rs	0.00%	9 Missing ⚠️
src/lang/property_lowering/compatibility.rs	96.26%	8 Missing ⚠️
src/lang/php.rs	81.81%	6 Missing ⚠️
src/lang/mod.rs	93.93%	2 Missing ⚠️
src/lang/property_lowering/kotlin.rs	98.30%	2 Missing ⚠️
src/lang/property_lowering/php.rs	98.27%	2 Missing ⚠️
src/spec/property_spec.rs	99.16%	2 Missing ⚠️

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