[PHP] Store remote-to-local path mapper configuration

[adamziel]

Remote-to-local path mapping can now be stored in a processor cursor and recreated without callers unpacking its fields. Every configured path is base64-encoded in the cursor, so filesystem names remain arbitrary byte strings.

This is a prerequisite for resumable pull processors which map remote index entries after a process restart.

Testing

The mapper suite covers identity placement, remaps, followed-symlink placement, precedence, and a JSON round trip with non-UTF-8 path bytes.

Stacked on #596.

[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	6.61 s	6.20 s	⚪ +407 ms (+6.6%)	✓	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	2.54 s	2.55 s	⚪ -10 ms (-0.4%)	✓	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	9.15 s	8.75 s	⚪ +396 ms (+4.5%)

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

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

[adamziel]

Superseded by a single minimal PR based directly on trunk.