[KaiEureka]

Adds optional Session isolation selection to Team and Workflow calls. A Team can set a run default and role overrides; Workflow agents can inherit that default or override it per call. Existing use_worktrees and boolean isolation calls retain their defaults.

The implementation reuses the current environment-pool operations for shared workspaces, worktrees and caller-provided factories. Nested roles inherit their actual spawning parent's environment. Cleanup preserves source dependencies and shared aliases, and an isolated entry agent saves its patch before its workspace is reclaimed.

Functional validation covers real Git workspaces, custom providers, nested Team spawns, failed shared-child construction, cross-strategy cleanup and descriptor ownership. Independent review findings were reproduced, repaired and checked again. Ruff, import-linter and deptry pass. The complete GitHub Actions checks pass, including the Python 3.10–3.14 suites, distribution verification, macOS tests and documentation translation checks.

This is the first part of the runtime feature series #241, #242, #243 and #244. It provides the environment selection used by the following Docker and managed Workflow changes.