feat(lsp-mcp): permanent pinned toolchain presets (rust-analyzer standing) (#76)

Stops the recurring re-assembly of the Rust LSP every session.

## What
- `lsp-mcp` `lsp_start` now accepts `{"preset":"rust"}` → resolves to
the canonical pinned rust-analyzer
(`/dev/tools/.../cargo-home/bin/rust-analyzer`). Backward compatible:
explicit `command` still wins.
- Root cause of the recurring pain: that path was a rustup *proxy with
no component installed*. Installed it (rust-analyzer 1.95.0).
- `cartridges/lsp-mcp/presets.json` — pinned presets (only
verified-installed servers; no unresolved entries).
- `.machine_readable/dev-toolchain.a2ml` — single source of truth for
the whole standing loop (rust lsp/build/lint/test, zig, julia, idris)
with verified paths. LSP wired now; bsp-mcp/dap-mcp adopt the same
pattern (declared, honest).
- `cartridge.json` schema updated (`preset` input; one of
command|preset).

## Verified
`deno check` clean; functional: preset rust→200 starts rust-analyzer,
bad preset→helpful 400, no-args→400, explicit command→200 (compat).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

.machine_readable/dev-toolchain.a2ml

@@ -0,0 +1,49 @@
+# SPDX-License-Identifier: PMPL-1.0-or-later
+# Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+#
+# BoJ Server — Permanent Dev-Toolchain Manifest
+#
+# Single source of truth for the standing local dev loop so it NEVER has to be
+# re-assembled per session. Paths are the canonical /dev/tools toolchain and
+# are verified-present (do not list a tool that is not actually installed —
+# an unresolved entry is worse than none).
+#
+# Wired NOW: the LSP row is live via `cartridges/lsp-mcp/presets.json`
+#   (lsp_start {"preset":"rust"} → rust-analyzer, no per-use wiring).
+# Adoption path: bsp-mcp (build), dap-mcp (debug) and a lint surface should
+#   read this same manifest for their Rust/Zig/Julia/Idris presets — same
+#   pattern as lsp-mcp. Declared here so the contract exists before the wiring.
+
+@canonical-location: `.machine_readable/dev-toolchain.a2ml`
+
+[authorization]
+standing = true
+note = "Owner standing authorization (2026-05-18): use these boj dev-loop capabilities on demand without asking for permission."
+
+[rust]
+lsp        = "/home/hyperpolymath/dev/tools/languages/rust/cargo-home/bin/rust-analyzer"   # verified: rust-analyzer 1.95.0 (rustup component)
+cargo      = "/home/hyperpolymath/dev/tools/languages/rust/cargo-home/bin/cargo"            # verified: cargo 1.95.0
+build      = "cargo build"
+check      = "cargo check"
+lint       = "cargo clippy --all-targets -- -D warnings"
+test       = "cargo test"
+debug      = "rust-gdb / lldb via dap-mcp"   # dap-mcp adoption pending
+env        = { CARGO_HOME = "/home/hyperpolymath/dev/tools/languages/rust/cargo-home", RUSTUP_HOME = "/home/hyperpolymath/dev/tools/languages/rust/rustup-home" }
+wired_lsp  = true   # cartridges/lsp-mcp/presets.json -> preset "rust"
+
+[zig]
+toolchain  = "zig 0.15.2"   # verified on PATH
+build      = "zig build"
+test       = "zig build test"
+wired_lsp  = false   # zls not installed; do NOT add an lsp preset until it is
+
+[julia]
+launcher   = "/home/hyperpolymath/dev/tools/languages/julia/juliaup-home/bin/julia"   # verified: 1.12.6 (release) / 1.10.11 (lts)
+test       = "julia --project=. -e 'using Pkg; Pkg.test()'"
+instantiate= "julia --project=. -e 'using Pkg; Pkg.instantiate()'"
+quality    = "Aqua.test_all + JET (when wired in a package's test deps)"
+wired_lsp  = false   # no julia LSP installed yet
+
+[idris2]
+check      = "/home/hyperpolymath/dev/tools/provers/idris2/0.8.0/bin/idris2 --check"   # verified: Idris2 0.8.0
+wired_lsp  = false   # idris2-lsp not installed yet

cartridges/lsp-mcp/cartridge.json

@@ -29,23 +29,25 @@
         "properties": {
           "command": {
             "type": "string",
-            "description": "Language server executable (e.g. 'rust-analyzer', 'affinescript server --stdio', 'clangd')"
+            "description": "Language server executable (e.g. 'rust-analyzer', 'affinescript server --stdio', 'clangd'). Optional when `preset` is given."
+          },
+          "preset": {
+            "type": "string",
+            "description": "Permanent pinned toolchain preset from presets.json (e.g. 'rust' → the canonical rust-analyzer at /dev/tools). Use this instead of re-specifying the command/path every session. One of `command` or `preset` is required; an explicit `command` overrides the preset."
           },
           "args": {
             "type": "array",
             "items": {
               "type": "string"
             },
-            "description": "Additional command arguments"
+            "description": "Additional command arguments (appended after any preset args)"
           },
           "workspace_root": {
             "type": "string",
             "description": "Workspace root directory path"
           }
         },
-        "required": [
-          "command"
-        ]
+        "required": []
       }
     },
     {

cartridges/lsp-mcp/mod.js

@@ -159,6 +159,21 @@ function getSession(session_id) {
   return entry;
 }
 
+// Permanent pinned toolchain presets (presets.json, co-located). Lets callers
+// pass {preset:"rust"} instead of re-specifying the rust-analyzer path every
+// time. Loaded once, lazily; missing/invalid file degrades to "no presets".
+let _presets = null;
+async function loadPresets() {
+  if (_presets) return _presets;
+  try {
+    const txt = await Deno.readTextFile(new URL("./presets.json", import.meta.url));
+    _presets = JSON.parse(txt).presets ?? {};
+  } catch {
+    _presets = {};
+  }
+  return _presets;
+}
+
 // ---------------------------------------------------------------------------
 // Tool handlers
 // ---------------------------------------------------------------------------
@@ -168,8 +183,21 @@ export async function handleTool(toolName, args) {
 
     // -- lsp_start -----------------------------------------------------------
     case "lsp_start": {
-      const { command, args: extraArgs = [], workspace_root } = args;
-      if (!command) return { status: 400, data: { error: "command is required" } };
+      let { command, preset, args: extraArgs = [], workspace_root } = args;
+
+      // Resolve a permanent pinned preset (e.g. "rust" → rust-analyzer) so
+      // callers never re-assemble the toolchain. Explicit `command` still
+      // wins and stays fully backward-compatible.
+      if (!command && preset) {
+        const presets = await loadPresets();
+        const p = presets[preset];
+        if (!p) {
+          return { status: 400, data: { error: `Unknown preset '${preset}'. Available: ${Object.keys(presets).join(", ") || "(none)"}` } };
+        }
+        command = p.command;
+        if (Array.isArray(p.args) && p.args.length) extraArgs = [...p.args, ...extraArgs];
+      }
+      if (!command) return { status: 400, data: { error: "command or preset is required" } };
 
       const cmdParts = command.trim().split(/\s+/);
       const proc = new Deno.Command(cmdParts[0], {

cartridges/lsp-mcp/presets.json

@@ -0,0 +1,14 @@
+{
+  "$schema": "https://boj.dev/schemas/lsp-presets/v1.json",
+  "spdx": "PMPL-1.0-or-later",
+  "copyright": "Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>",
+  "_doc": "Permanent, pinned LSP server presets. lsp_start accepts {\"preset\":\"rust\"} instead of re-specifying the command/path every time. Absolute paths point at the canonical /dev/tools toolchain. Only presets whose server binary is actually installed and verified are listed here — do NOT add a preset for a server that is not present (an unresolved preset is worse than no preset).",
+  "presets": {
+    "rust": {
+      "command": "/home/hyperpolymath/dev/tools/languages/rust/cargo-home/bin/rust-analyzer",
+      "args": [],
+      "language_id": "rust",
+      "verified": "rust-analyzer 1.95.0 (rustup component, stable toolchain)"
+    }
+  }
+}