feat(dispatch): Compact Instructions block for lineage forks (closes #27)

[Srinivasan8888]

Problem

A lineage fork (evo dispatch forking from a committed parent experiment's own session) inherits the parent's transcript. The worker protocol therefore reaches the child only through that cached context. On long ancestor chains, Claude Code auto-compacts the older portion of the transcript and can summarize the protocol away.

The existing LINEAGE_EXECUTE_USER_PROMPT_TEMPLATE only hints at this — "re-read the protocol from <path> if you can no longer see it." As #27 notes, that's a hint, not a guarantee.

Fix

Add a # Compact Instructions block to the lineage execute prompt that marks the load-bearing context as preserve-on-summary, exactly as proposed in #27:

# Compact Instructions

Preserve when summarizing:
- current exp_id, hypothesis, parent_commit
- worker protocol; `evo run` is terminal
- pointer-trace references and gate semantics

May be discarded:
- older file reads (recoverable via `evo get` / Read)
- older benchmark output detail
- failed tool calls from prior attempts

The block is injected only into lineage forks (render_execute_prompt(..., lineage=True)). Fresh explorer children receive the protocol in the current turn and don't inherit a long transcript, so they intentionally do not carry the block.

Tests

Added tests/unit/test_compact_instructions.py (TDD — written failing first):

• lineage prompt includes the Compact Instructions header + Preserve when summarizing
• lineage prompt pins the specific load-bearing items (exp_id, hypothesis, parent_commit, worker protocol, evo run is terminal, gate)
• non-lineage prompt omits the block

tests/unit (excluding the three Rust-evo-hook-drain-binary tests, which are environmental on a machine without a Rust toolchain): 801 passed, 4 skipped. All existing test_dispatch.py tests pass unchanged.

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.