fix(jupyter-notebook): preserve stream overwrite cursors

[Ricardo-M-L]

Plugin type (required)

• UI Plugin
• Standard plugin
• Not applicable

Affected plugin name: jupyter-notebook

What

Preserve the stream write cursor between kernel messages. The current reducer normalizes each chunk, then appends the next chunk to the normalized text, losing the cursor after a carriage return. Hello\rWo renders as Wollo in one message, but Hello\rW followed by o renders as Welloo.

• Keep bounded, in-memory cursor and logical-line-start state separately from notebook outputs.
• Preserve overwrite positions across stream chunks without persisting internal state in .ipynb files.
• Reset continuation when output identity changes, outputs are cleared, a cell is rerun/reloaded, or a cell is removed.
• Keep truncation-marker newlines out of logical cursor positioning.
• Bump manifest, marketplace, source package and protocol versions from 0.1.0 to 0.1.1; update both README languages.

No new dependencies, permissions, network services, or changes to execution approvals. Existing Jupyter access and notebook writes are unchanged. No generated distribution files are committed.

Verification

• Unit tests: 44 passed. Includes every split point and single-character chunks for CR/CRLF/backspace examples, output interleaving, clear_output, immutable branches, and bounded long output.
• Real Jupyter integration: 15 passed. Explicit flushes send the regression across kernel messages; two executions validate cursor reset, and saved notebook data contains only standard stream fields.
• Built MCP stdio smoke: passed.
• Chrome panel through the official AppBridge + real Jupyter: passed (test:e2e). This is not a ZCode Desktop installation test.
• Root pnpm test, pnpm typecheck, pnpm lint: passed (12 lint warnings in unrelated existing files; touched files have none).
• python3 scripts/validate.py: all 45 plugins validated.
• git diff --check: passed.

Outstanding / draft boundary

This is a draft pending complete repository packaging and real ZCode Desktop installation verification. pnpm build stops in the unrelated photocraft snapshot build because the pinned Rust WASM target / Trunk toolchain is missing; consequently build_dist.py correctly rejects the incomplete build. The Jupyter package itself builds and its integration/smoke/browser tests pass. No build checks were bypassed, no user plugin configuration was changed, and Desktop verification is not claimed.

Self-check

• Existing plugin ownership retained; only this plugin and its marketplace version changed
• Plugin type and name declared
• Immutable installable-content version bumped consistently
• Equivalent English / Chinese README update
• No secrets, private endpoints, machine paths, or generated artifacts
• Existing dependencies and side effects unchanged
• Validator passes
• Full root build and build_dist pass
• Installed and exercised in ZCode Desktop