fix(state): use merge_dicts reducer for scratchpad to prevent key loss on concurrent writes

[citizen204]

Summary

When the executor calls save_note multiple times in the same
executor_tools superstep (i.e. the LLM emits several tool calls at
once), every save_note invocation reads the same base
state.scratchpad and produces a complete merged-copy update:

updated_scratchpad = {**state.scratchpad, key: content}

The previous take_last reducer then keeps only the last update,
silently discarding all keys written by earlier calls in the same
batch. With merge_dicts as the reducer, LangGraph accumulates each
branch's output via {**a, **b}, so every key written by every tool
call in the same superstep survives.

Fixes #208

Changes

• minitap/mobile_use/graph/state.py: add merge_dicts helper and use
  it as the reducer for scratchpad instead of take_last

Summary by CodeRabbit

• Bug Fixes
  • Updated how saved app state is combined so new values can be merged into existing stored data instead of replacing it entirely.
  • Improved persistence for the scratchpad, helping preserve previously stored entries while applying updates.

[coderabbitai]

📝 Walkthrough

Walkthrough

This PR adds a dictionary merge helper and changes State.scratchpad to merge incoming updates instead of replacing the whole dict.

Changes

Scratchpad merge behavior

Layer / File(s)	Summary
Dict merge helper and scratchpad reducer minitap/mobile_use/graph/state.py	Adds merge_dicts(a, b) to combine two dictionaries with b overriding a, and updates State.scratchpad to use that reducer.

🎯 1 (Trivial) | ⏱️ ~2 minutes

🐇 I hop through notes, one key at a time,
Two paws of updates now mingle in rhyme.
No scratchpad crumbs get lost in the night,
Merge, little burrow, and keep them all right. 🥕

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 66.67% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately summarizes the scratchpad reducer change and its purpose.
Linked Issues check	✅ Passed	It satisfies the issue's immediate objective by merging concurrent scratchpad updates instead of replacing them.
Out of Scope Changes check	✅ Passed	The change stays focused on the scratchpad reducer and does not introduce unrelated scope.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[coderabbitai]

🧹 Nitpick comments (1)

minitap/mobile_use/graph/state.py (1)

21-21: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Remove the redundant docstring on Line 21.

This sentence restates exactly what the implementation already makes obvious; prefer code clarity over explanatory restatement comments.

As per path instructions, "Comments: flag any comment that restates what the code already says."

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@minitap/mobile_use/graph/state.py` at line 21, Remove the redundant docstring
in the state module: the brief description on the merge helper is just restating
what the implementation already makes obvious. Delete the docstring near the
dict-merge logic in state.py and leave the function/class code unchanged so the
intent comes from the code itself.

Source: Path instructions

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@minitap/mobile_use/graph/state.py`:
- Line 21: Remove the redundant docstring in the state module: the brief
description on the merge helper is just restating what the implementation
already makes obvious. Delete the docstring near the dict-merge logic in
state.py and leave the function/class code unchanged so the intent comes from
the code itself.

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a3b9d1d8-c220-40d9-bb25-2c8790ed1074

📥 Commits

Reviewing files that changed from the base of the PR and between 47cce16 and 7a57c9b.

📒 Files selected for processing (1)

• minitap/mobile_use/graph/state.py

[plfavreau]

Thank you @citizen204 for your contribution ! Merging your PR.