[codex] Bound data declaration and analysis queries

[farvend]

What changed

• Limit default get_data_decl previews to 4096 bytes and explicit reads to 1 MiB.
• Report size_known, bytes_read, and truncated.
• Apply data pagination during iteration.
• Remove program-wide IL and data-variable scans from size and symbol resolution.

Why

Large data declarations and fallback heuristics could scan an entire database or return unbounded responses.

Impact

Data inspection has predictable response sizes and avoids expensive whole-program work.

Validation

• python -B -m unittest discover -s tests -p "test_*.py" (7 tests)
• npm run build