feat: support windowed multi-query memory search

[jif-oai]

Why

Memory search currently supports either independent substring matches or requiring every query to appear on the same line. That is too restrictive for memory files where related terms often land on nearby lines in the same note or bullet block.

What changed

• Replace the old all match mode with explicit tagged modes: all_on_same_line and all_within_lines { line_count }.
• Add windowed matching in codex-rs/memories/mcp/src/local.rs so callers can require every query to appear within a bounded line range while returning only the minimal qualifying windows.
• Reject invalid zero-width windows and update the MCP tool description plus argument parsing to expose the new mode.
• Add coverage for same-line matching, windowed matching, and invalid line_count input.

Verification

• Added targeted coverage in codex-rs/memories/mcp/src/local_tests.rs for search_supports_all_within_lines_match_mode and search_rejects_zero_line_window.
• Added server-side parsing coverage in codex-rs/memories/mcp/src/server.rs for search_args_accept_windowed_all_match_mode.

[jif-oai]

@codex review

[chatgpt-codex-connector]

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