docs(plugin): bring boundary text in line with the implementation

Comments that pointed at design notes kept outside the repository are dead
ends for anyone reading only the tree, so what each of them explained now
lives in a tagged TODO at the site it applies to. Several of those sites
also stated something the implementation does not do, and the TODOs record
the actual gap instead: the two halves of the codec recognize handle
descriptors by different rules, the scripts Command path drops the exception
class and collects output in a BufferedOutput that cannot carry an
interactive command, find_shortest_path panics where PHP throws, and the
package dispatch hand-rolls the variant selection AnyPackage should own.

The classifier document likewise described rust-snapshot,
plugin-constructible and several of the open questions as designed rather
than as built.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/crates/shirabe-php-rpc/php/worker.php b/crates/shirabe-php-rpc/php/worker.php
index 164d73ea..6ed5df40 100644
--- a/crates/shirabe-php-rpc/php/worker.php
+++ b/crates/shirabe-php-rpc/php/worker.php
@@ -267,6 +267,12 @@ final class ShirabeRpcRuntime
     /**
      * Converts a decoded wire value: handle descriptor arrays become live objects. A
      * materialized value arrives as a real instance already, revived by unserialize().
+     *
+     * TODO(type-model): a descriptor travels in-band as a plain array, so its exact key set is
+     * the only thing separating it from plugin data of the same shape. Every check below except
+     * __pclass matches on the reserved key alone, so an array a plugin built with a __rhandle or
+     * __phandle key of its own is read as a handle rather than kept as data. The Rust half
+     * (`decode_handle` in `src/value.rs`) matches the whole key set, and diverges the other way.
      */
     public static function fromWire($value)
     {
@@ -806,7 +812,7 @@ ShirabeRpcRuntime::$dispatch = [
     },
     // An already-fulfilled promise for a Rust-side call whose PHP signature declares
     // PromiseInterface. The Rust future ran to completion before this is called, so there is
-    // nothing left to defer; see .ken/plugin-arch/design.md §10.1.6.
+    // nothing left to defer.
     '__shirabe_resolved_promise' => static function ($args) {
         if (!function_exists('React\\Promise\\resolve')) {
             throw new RuntimeException(