fix(hooks): reset reminder counters after a successful Codex Serena call

Codex's documented hook wiring only routes `serena-hooks remind` through
PreToolUse on the `Bash` matcher, so `ToolUseCounter.update()`'s
reset-on-Serena-tool-use branch is never reached there: it only fires when
`remind` itself is invoked for a `mcp__serena__*` tool name, which the
Bash-only matcher excludes. Reminder counters therefore never clear after a
successful Serena call, and an unrelated grep/read burst afterwards can trip
the deny threshold on state that should have been reset.

Add a `serena-hooks reset` command, wired to PostToolUse on Serena's own
tools, that resets the counters after a successful call. Gated on the call
having succeeded (`tool_response` carrying no `isError: true`, the MCP
`tools/call` result shape) so a failed Serena call does not mask a real
grep/read streak, per the issue's own acceptance criteria. The symbolic-tool
classification is shared with the existing PreToolUse hook via a small
extracted helper so both agree on what counts as a Serena tool.

Fixes #1852

docs/02-usage/030_clients.md

@@ -344,6 +344,17 @@ Then create `~/.codex/hooks.json` with the following content:
                 ]
             }
         ],
+        "PostToolUse": [
+            {
+                "matcher": "^mcp__serena__.*$",
+                "hooks": [
+                    {
+                        "type": "command",
+                        "command": "serena-hooks reset --client=codex"
+                    }
+                ]
+            }
+        ],
         "SessionStart": [
             {
                 "matcher": "startup|resume",
@@ -381,10 +392,15 @@ The hooks will:
   when a Codex session starts or resumes.
 - **`remind`**: Nudge the agent to use Serena's symbolic tools when it makes too many consecutive
   code-search or code-file-read calls without using Serena tools in between.
+- **`reset`**: Clear the reminder counters after a successful Serena symbolic tool call, so using
+  Serena's tools starts a fresh count instead of leaving the prior grep/read streak in place.
 - **`cleanup`**: Clean up hook session data when the session ends.
 
-The `PreToolUse` matcher is intentionally restricted to `Bash`. The Serena reminder hook for Codex
-tracks shell-based grep and code-file reads, so running it for every tool call is unnecessary.
+The `PreToolUse` matcher is intentionally restricted to `Bash`: the reminder hook tracks shell-based
+grep and code-file reads, so running it for every tool call is unnecessary. That matcher never sees
+`mcp__serena__*` tool names, though, so it cannot also perform the counter reset on Serena tool use
+the way it does for clients whose `PreToolUse` hook observes every tool call. The separate `reset`
+hook above, matched to `PostToolUse` on Serena's own tools, covers that case for Codex instead.
 
 ## Grok