Add .loop-build harness and IntelliJ project configuration files

.loop-build/prompts/executor.md

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+# loop-build Executor Prompt
+
+## Inputs
+
+- `current_task`: contents of `.loop-build/state/current_task.json`
+- `step_id`: current step id
+- `context_snippets`: short file snippets around affected areas
+- `verify_summary`: latest verify summary if any
+
+## Task
+
+Produce a strictly scoped execution plan for exactly **one** step.
+
+Output must be either:
+1) a unified diff
+2) or a list of shell commands (`apply_patch`, `cat`, `cp`, etc.)
+
+No commands or patch may touch more than 2 files.
+
+If returning commands:
+- they are for the single step only
+- include only minimal verification command needed for this step
+- all non-read actions require explicit approval in harness policy
+
+Example accepted outputs:
+
+- `git diff` style block
+- command list with one command per line
+
+Disallowed:
+- Full file dumps
+- Multiple-step execution beyond the selected step
+- Extra unrelated refactors
+- Implicitly chaining future step actions