fix(cc-config): stop pinning CLAUDE_CONFIG_DIR when CLAUDE_HOME is unset

runClaude() unconditionally set CLAUDE_CONFIG_DIR to getClaudeHome()
(~/.claude), so the CLI wrote ~/.claude/.claude.json — a file
cc-discovery.getClaudeJsonPath() never reads (it reads ~/.claude.json,
beside ~/.claude/, by design). Every default-install MCP add/remove and
plugin/marketplace mutation was inert: add toasted success and vanished on
refetch, remove 422'd for every server the panel lists.

With CLAUDE_HOME unset (the default), leave CLAUDE_CONFIG_DIR unset too —
the CLI's own default config dir already lines up with what cc-discovery
reads, so alignment comes from doing nothing. Only pin it when the operator
explicitly set CLAUDE_HOME, which is the one case the pin is meant for.
Left a residual, documented at both sites: with CLAUDE_HOME set, reads still
come from $HOME/.claude.json while the CLI writes
<CLAUDE_HOME>/.claude.json — a split predating this task, affecting a
configuration nobody here runs.

New tests pin the env contract directly (no real CLI needed): runClaude
must not set CLAUDE_CONFIG_DIR when CLAUDE_HOME is absent, and must set it
to CLAUDE_HOME's value when present.

server/lib/cc-plugin-cli.js

@@ -131,15 +131,27 @@ function serialize(fn) {
 function runClaude(args, opts = {}) {
   const timeout = opts.timeoutMs || DEFAULT_TIMEOUT_MS;
   return new Promise((resolve, reject) => {
+    // Only pin CLAUDE_CONFIG_DIR when the operator explicitly set CLAUDE_HOME
+    // (a non-default install). Left unset, the CLI's own default config dir
+    // is `~/.claude` and it writes `.claude.json` NEXT TO it (`~/.claude.json`)
+    // — the exact file cc-discovery.getClaudeJsonPath() reads (see that
+    // function's own comment). Pinning CLAUDE_CONFIG_DIR unconditionally to
+    // getClaudeHome() made the CLI write `~/.claude/.claude.json` instead —
+    // a file nothing reads — so every default-install add/remove was inert.
+    // When CLAUDE_HOME IS set, this still pins it, but note the residual:
+    // cc-discovery's read stays pinned to $HOME/.claude.json regardless (see
+    // getClaudeJsonPath's comment) while the CLI then writes
+    // <CLAUDE_HOME>/.claude.json — a pre-existing split this task does not
+    // attempt to fix, since no install in this repo runs with CLAUDE_HOME set.
+    const env = { ...process.env };
+    if (process.env.CLAUDE_HOME) env.CLAUDE_CONFIG_DIR = getClaudeHome();
     const child = execFile(
       "claude",
       args,
       {
         timeout,
         maxBuffer: MAX_OUTPUT_BYTES,
-        // Pin the CLI to the same config dir cc-discovery reads, so a write
-        // made here is a write the dashboard can see.
-        env: { ...process.env, CLAUDE_CONFIG_DIR: getClaudeHome() },
+        env,
       },
       (err, stdout, stderr) => {
         const out = String(stdout || "");