feat(agent): isolate agent cwd in .ideai/run/<id> to kill convention-file collisions

ARCHITECTURE §14.1: an agent's PTY cwd is now its own
`<project_root>/.ideai/run/<agent-id>/` directory, never the project root, so
N agents of the same profile no longer collide on a single conventional file
(CLAUDE.md/AGENTS.md/...).

- profile: cwd_template is now "{agentRunDir}" (built-in catalogue + docs).
- runtime: resolve_cwd substitutes {agentRunDir} (legacy {projectRoot} kept).
- LaunchAgent: computes + creates the run dir via FileSystem::create_dir_all,
  passes it as the cwd base to the pure prepare_invocation. Contract chosen:
  pass run_dir as the `cwd` argument (no PreparedContext change) — keeps
  prepare_invocation pure, I/O stays in the use case.
- convention file is generated by IdeA inside the run dir via a pure
  compose_convention_file(project_root, agent_md): absolute project-root header
  + agent persona (extensible for skills, §14.2).
- .gitignore: ignore .ideai/run/.
- run-dir cleanup left as a TODO (FileSystem port exposes no delete).

Tests: anti-collision (2 agents -> 2 distinct cwd, 2 distinct convention files,
none at root), run-dir creation order, composed convention file; pure unit
tests for agent_run_dir + compose_convention_file; runtime {agentRunDir}
substitution. cargo test --workspace + clippy -D warnings green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/infrastructure/src/runtime/mod.rs

@@ -80,16 +80,23 @@ impl CliAgentRuntime {
         })
     }
 
-    /// Resolves the profile's `cwd_template` against the project root.
+    /// Resolves the profile's `cwd_template` against the supplied `base` cwd.
     ///
-    /// The only recognised placeholder is `{projectRoot}` (CONTEXT §9). An empty
-    /// template defaults to the project root itself.
-    fn resolve_cwd(profile: &AgentProfile, root: &ProjectPath) -> Result<ProjectPath, RuntimeError> {
+    /// The base is the agent's **run directory** (`.ideai/run/<agent-id>/`),
+    /// already computed (and created) by `LaunchAgent` and passed as the `cwd`
+    /// argument of [`prepare_invocation`](AgentRuntime::prepare_invocation). The
+    /// recognised placeholder is `{agentRunDir}` (ARCHITECTURE §14.1); the legacy
+    /// `{projectRoot}` is still substituted with the same base for backwards
+    /// compatibility (the caller always passes the run dir now). An empty template
+    /// defaults to the base itself.
+    fn resolve_cwd(profile: &AgentProfile, base: &ProjectPath) -> Result<ProjectPath, RuntimeError> {
         let template = profile.cwd_template.trim();
         if template.is_empty() {
-            return Ok(root.clone());
+            return Ok(base.clone());
         }
-        let resolved = template.replace("{projectRoot}", root.as_str());
+        let resolved = template
+            .replace("{agentRunDir}", base.as_str())
+            .replace("{projectRoot}", base.as_str());
         ProjectPath::new(resolved).map_err(|e| RuntimeError::Invocation(e.to_string()))
     }