[PHP] Share resumable file sync patch processing

[adamziel]

Adds one resumable processor for building a fresh local index and planning a patch against a saved index.

Push keeps its current path lists and progress labels. PushPlan now consumes operations from the shared processor instead of coordinating FreshLocalIndexProcessor and FileSyncPatchPlanner itself.

The two start methods make the patch direction explicit:

// Saved index -> current local tree. Used by push.
$processor = FileSyncPatchProcessor::start_to_fresh_local_tree(
	$work_directory,
	$filesystem_root,
	$saved_local_index,
	$storage_path
);

// Current local tree -> saved index. Used by mirror pull in the next PR.
$processor = FileSyncPatchProcessor::start_from_fresh_local_tree(
	$work_directory,
	$filesystem_root,
	$saved_local_index,
	$storage_path
);

The processor owns the scan, sort, patch planner, and their complete cursor. Callers store that cursor unchanged and consume one operation per planning step.

This also keeps selection roots safe in JSON cursors and lets a selected subtree be deleted without crossing a nested include or exclusion boundary.

Testing

The processor, planner, PushPlan, and real push endpoint suites cover both patch directions, interruption at every internal phase, arbitrary path bytes, exclusions, progress, and process resume.

[github-actions]

Pull pipeline performance — large-directory

Site: large-directory · 2,000+ plus targeted file-transfer scenarios files · 10,000 posts · 25,000 postmeta · PHP 8.5.9

Stage	PR	trunk	Δ	Status	Details
playground-sqlite-db-pull	9.59 s	9.80 s	⚪ -214 ms (-2.2%)	✓	condition=db-pull in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=lexer native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=selected trunk: condition=db-pull in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=lexer native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=selected
playground-sqlite-db-apply	3.72 s	3.80 s	⚪ -85 ms (-2.2%)	✓	condition=db-apply to SQLite in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=parser native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=verified native_ast=WP_MySQL_Native_Parser_Node sqlite_driver_parser=verified trunk: condition=db-apply to SQLite in PHP.wasm runtime=php.wasm 8.3 wp_mysql_parser=enabled mode=parser native_lexer=verified native_token_stream=WP_MySQL_Native_Token_Stream native_token_count=18 native_parser=verified native_ast=WP_MySQL_Native_Parser_Node sqlite_driver_parser=verified
Total	13.30 s	13.60 s	⚪ -299 ms (-2.2%)

_{Numbers carry runner noise; treat single-run deltas as directional, not authoritative.}

_{📈 Trunk performance history — commit-by-commit timeline.}