v0.12.0

Minor Changes

• 1e15922: Bump default Claude Code model from claude-opus-4-7 to claude-opus-4-8. The new default applies to the DEFAULT_MODEL constant, the claude-code agent entry surfaced by sandcastle init, and the scaffolded templates (blank, parallel-planner, parallel-planner-with-review). Passing an explicit model to claudeCode(...) is unaffected.
• 0f577a4: Add sandbox.exec(command, options?) to the Sandbox handle returned by createSandbox() (and by worktree.createSandbox()). The method delegates to the provider handle's exec() and returns the full ExecResult — non-zero exitCode is surfaced, not thrown — so harnesses can run shell commands (tests, lints, custom verification gates) directly in the same warm sandbox between run() calls without reaching for the underlying provider handle. cwd defaults to the sandbox repo path so behavior is consistent across providers; pass cwd to override.

Patch Changes

• c505d49: Fix file-mode logging so streamed agent text flows as contiguous prose instead of one chunk per line. Added a dedicated textChunk streaming method to the display service (raw, no implied newline in file mode) and pointed the text-delta buffer at it, leaving the line-oriented text() for discrete entries like context-window summaries. Structured entries (tool calls, status, summaries) still always begin on their own line, even when they immediately follow a mid-line streamed chunk.