fix(sourcehunt): file reading updates to reduce stalling

[jorge-garcia-le]

Summary

• Make read_file return complete source lines with an explicit continuation line and EOF status based on delivered content.
• Reduce the default read window to 100 lines and align tool-start range reporting.
• Track source lines actually delivered to each hunter in a merged, run-wide coverage ledger. Use the same ledger for read-overlap metadata and stall progress, normalize repository-relative and /workspace paths, and retain coverage through context compaction.
• Check every fully covered read_file or read_function request. Give the model one retry per turn, then block another covered read without refresh=true before the tool runs. Show all merged coverage ranges for the file and its total line count in the warning. Explicit refreshes remain available and add no new source coverage or stall progress.
• Route successful read_function calls through the same 12,000-character source view, delivered-line coverage ledger, and stall-progress accounting as read_file. Resolve function names through the callgraph, and direct truncated function reads to the next read_file range.
• Add regression coverage for clipping, EOF, continuation, path aliases, compaction, mixed tool batches, retry accounting, covered reads of different ranges in the same file, file-wide warning text, and function reads that are new, covered, long, missing, or ambiguous.

Evaluation comparison

Using qwen3.8-27b

CVE	Main branch	Current branch
CVE-2026-32316	Fail; stalled	Pass; completed
CVE-2026-44420	Fail; stalled	Pass; completed
CVE-2026-45796	Fail; stalled	Pass; completed
CVE-2026-27775	Pass; stalled	Pass; completed
CVE-2026-41401	Fail; stalled	Fail; completed with an unrelated finding