Move docs/ package mirror into document-navigator plugin

Relocate the ~6k-file docs tree from the repo root into
plugins/document-navigator/docs/ so the plugin is self-contained and
portable. docs/superpowers/ (specs and plans) stays at the repo root.

Moved via cp+rm rather than git mv because directory rename() fails with
EPERM on this WSL /mnt DrvFs mount; git rename-detection pairs the
identical-content files at commit time.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/document-navigator/docs/api-stack/api/api-sandbox-wasm-host-bridge/src/abi-wasi-stdio/wasi-stdio-validate.md

@@ -0,0 +1,101 @@
+# `wasi-stdio-validate`
+
+## Purpose
+
+ABI surface validator for the WASI-stdio variant. Inspects a
+`WebAssembly.Module`'s imports and exports BEFORE instantiation and
+raises `SAND_WASM_BRIDGE.INVALID_PLUGIN_SURFACE` if the module is
+missing any of the five required WASI imports
+(`wasi_snapshot_preview1.{fd_read, fd_write, environ_get,
+environ_sizes_get, proc_exit}`) OR the two required exports (`memory`,
+`_start`). The check is the WASI-stdio mirror of `validateWasmAbi`
+in `abi-direct/wasm-abi/`; it does NOT require the six
+`__suaveplan_*` direct-variant exports because Javy-compiled plugins
+cannot emit them.
+
+## Features
+
+- Module-level (pre-instantiation) check — operators see the failure
+  before the host commits to instantiating the plugin.
+- Both required imports and required exports are validated in a single
+  pass; `context.missing` carries the sorted union of absent symbols.
+- Namespace-qualified diagnostic for imports
+  (`wasi_snapshot_preview1.fd_read`) vs bare for exports (`_start`)
+  makes the absent surface obvious at a glance.
+- The required-symbol lists are sorted constants so a future addition
+  surfaces as a typecheck divergence rather than a silent drift.
+
+## Usage: Basic
+
+```ts
+import { validateWasiStdioAbi } from
+    "@suaveplan/api-sandbox-wasm-host-bridge/abi-wasi-stdio";
+
+declare const module: WebAssembly.Module;
+validateWasiStdioAbi(module, "example");
+// Throws SandboxWasmBridgeError on missing surface.
+```
+
+## Usage: Advanced
+
+```ts
+import { validateWasiStdioAbi } from
+    "@suaveplan/api-sandbox-wasm-host-bridge/abi-wasi-stdio";
+import {
+    SAND_WASM_BRIDGE_CODES,
+    SandboxWasmBridgeError,
+} from "@suaveplan/api-sandbox-wasm-host-bridge/error-codes";
+
+declare const module: WebAssembly.Module;
+try {
+    validateWasiStdioAbi(module, "billing");
+} catch (err) {
+    if (
+        err instanceof SandboxWasmBridgeError &&
+        err.code === SAND_WASM_BRIDGE_CODES.INVALID_PLUGIN_SURFACE
+    ) {
+        const missing = (err.context as { missing?: readonly string[] })
+            .missing;
+        // missing → ["_start"]  OR  ["wasi_snapshot_preview1.fd_read", ...]
+        void missing;
+    }
+}
+```
+
+## API Reference
+
+### `validateWasiStdioAbi(module, pluginName): void`
+
+- `module: WebAssembly.Module` — pre-compiled module under inspection.
+- `pluginName: string` — error-context label.
+
+Throws `SandboxWasmBridgeError` with code
+`SAND_WASM_BRIDGE.INVALID_PLUGIN_SURFACE` and
+`context.abiVariant = "wasi-stdio"` + sorted `context.missing`.
+
+### `REQUIRED_WASI_STDIO_IMPORTS: readonly string[]`
+
+Sorted list: `environ_get`, `environ_sizes_get`, `fd_read`, `fd_write`,
+`proc_exit`.
+
+### `REQUIRED_WASI_STDIO_EXPORTS: readonly string[]`
+
+Sorted list: `_start`, `memory`.
+
+## Implementation Notes
+
+- The validator walks `WebAssembly.Module.imports(module)` and
+  `WebAssembly.Module.exports(module)` once each — both are O(n) over
+  the module's metadata and never touch the linear memory. Running
+  them BEFORE instantiation costs effectively nothing.
+- The required-imports list is intentionally minimal: it captures the
+  five hooks any WASI-stdio guest MUST call. A guest that uses
+  additional WASI imports (e.g. `clock_time_get`, `random_get`) is
+  fine — those are wired by the runner but their absence is not a
+  surface error.
+- `context.abiVariant` carries the literal `"wasi-stdio"` string so
+  operators reading a stack trace can tell which variant raised
+  without inferring it from the plugin's manifest. The direct
+  validator does not set this field for the inverse reason: the
+  direct path is the default and the absence of the field implies
+  it.