fix(cc-config): .claude.json sits BESIDE ~/.claude by default, not inside it

The previous commit routed the read through getClaudeHome(), which appends
/.claude when CLAUDE_HOME is unset — pointing the dashboard at
~/.claude/.claude.json, a file the CLI never writes by default. Verified
against the real binary: with CLAUDE_CONFIG_DIR unset the CLI writes
$HOME/.claude.json; with it set, .claude.json sits flat inside that dir.
Branch on CLAUDE_HOME accordingly.

The test now drives a fake claude that writes where the real one does and
asserts getClaudeJsonPath() names that exact file, under both branches —
the previous test only restated the implementation.

openapi.yaml

@@ -2039,6 +2039,10 @@ components:
           type: string
           description: Where the definition was found, e.g. `~/.claude.json (top-level)`, `~/.claude.json (projects[<root>])`, or `~/.claude/settings.json`.
           example: ~/.claude.json (top-level)
+        removable:
+          type: boolean
+          description: False when no `claude mcp` scope can address this entry (currently only ~/.claude/settings.json-sourced servers), so POST /mcp/remove has no scope that would find it. Absent/true means removable.
+          example: true
         kind:
           type: string
           enum: