feat(php-shim): implement fopen-family stream API on PhpResource

Redesign PhpResource into a real stream handle (File/Memory backing with
tracked position, eof, closed state) and unify the whole fopen family
(fopen/fwrite/fread/fgets/fgetc/feof/fclose/ftell/fseek/rewind/fstat/
ftruncate/fflush and stream_get_contents/stream_copy_to_stream) on
&PhpResource, replacing the split PhpMixed/PhpResource APIs and their
todo!() stubs. fopen now returns Result; read functions stay String for
now (TODO(phase-e) to move to byte strings).

Propagate the signatures through callers: Process stdout/stderr, Cursor
input, curl header/body handles (extracted into typed maps keyed by job
id), Filesystem copy/safe_copy/files_are_equal, BufferIO, error_handler,
platform, perforce, zip. The proc_open pipe paths cannot carry a
PhpResource in a PhpMixed list, so they are left as todo!() with notes.

1 files changed, 2 insertions, 2 deletions

diff --git a/crates/shirabe-php-shim/src/process.rs b/crates/shirabe-php-shim/src/process.rs
index 8551d27..b47c579 100644
--- a/crates/shirabe-php-shim/src/process.rs
+++ b/crates/shirabe-php-shim/src/process.rs
@@ -210,8 +210,8 @@ pub fn posix_isatty(stream: PhpResource) -> bool {
         PhpResource::Stdin => std::io::stdin().is_terminal(),
         PhpResource::Stdout => std::io::stdout().is_terminal(),
         PhpResource::Stderr => std::io::stderr().is_terminal(),
-        // A regular file is never a tty.
-        PhpResource::File(_) => false,
+        // A regular file or in-memory stream is never a tty.
+        PhpResource::Stream(_) => false,
     }
 }