feat: flag unportable tool schemas in all three clients

Closes #1005

A tool schema can be perfectly legal JSON Schema and still be rejected by
the client the server is meant to run against — Go's `jsonschema` emits a
bare `true` for `interface{}`, which the SDK accepts and Claude Code
refuses with an opaque "Invalid input". The Inspector passed it through
silently.

Adds `core/json/schemaLint.ts`, a portability lint over a tool's
inputSchema/outputSchema, and surfaces one shared verdict everywhere:
the CLI's `--strict` report (exit 6 on an error-severity finding), the
TUI's tool list marker + detail pane, and the web Tools sidebar flag +
detail section.

Deliberately not a JSON Schema validator: a census of 617 public servers
found zero that fail the SDK's own parse, so a conformance check would
report nothing on real servers. Each rule is instead a construct that is
legal JSON Schema and known to be refused or mishandled by a shipping
client — a bare boolean in a schema position, an array-form `type`, a
remote `$ref`, a schema with no validation keyword, a non-object root.

`test-servers/configs/unportable-schemas-http.json` exercises every rule,
via a new `rawToolSchemas` override — the Zod-built presets cannot emit
any of these shapes, which is the same reason a real server only hits
this when its schemas come from another generator.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UL9retfvAXRgvi6EWk4SY4
Signed-off-by: cliffhall <cliff@futurescale.com>

test-servers/configs/unportable-schemas-http.json

@@ -0,0 +1,39 @@
+{
+  "serverInfo": {
+    "name": "unportable-schemas-showcase",
+    "version": "1.0.0"
+  },
+  "tools": [{ "preset": "echo" }, { "preset": "add" }, { "preset": "get_temp" }],
+  "rawToolSchemas": {
+    "echo": {
+      "inputSchema": {
+        "type": "object",
+        "properties": {
+          "message": { "type": "string" },
+          "show_ids": { "type": ["null", "boolean"] },
+          "opts": {}
+        }
+      },
+      "outputSchema": {
+        "type": "object",
+        "properties": {
+          "data": true,
+          "topic": { "type": "string" }
+        }
+      }
+    },
+    "add": {
+      "inputSchema": {
+        "type": "object",
+        "properties": {
+          "a": { "$ref": "https://example.com/schemas/number.json" },
+          "b": { "type": "number" }
+        }
+      }
+    }
+  },
+  "transport": {
+    "type": "streamable-http",
+    "port": 6603
+  }
+}