perf: Defer black import to first use

[KRRT7]

• Defer import black from module level to first use in answers.py and utils.py
• black (code formatter + transitive deps: pathspec, black.nodes, etc.) loaded on every import typeagent but only used in two cold formatting paths

black.format_str() is called in two places:

• create_context_prompt() in knowpro/answers.py — formats debug context for LLM prompts
• format_code() in aitools/utils.py — developer pretty-print utility

Neither runs during normal library operation. Moving the import inside each function eliminates ~78ms of transitive module loading from the import chain.

Benchmark

Azure Standard_D2s_v5 — 2 vCPU, 8 GiB RAM, Python 3.13

Import Time (hyperfine, warmup 5, min-runs 30)

Benchmark	Before	After	Speedup
import typeagent	791 ms ± 11 ms	713 ms ± 8 ms	1.11x

Offline E2E Test Suite (hyperfine, warmup 2, min-runs 10)

Benchmark	Before	After	Speedup
69 offline tests	5.72 s ± 90 ms	5.60 s ± 98 ms	1.02x

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Generated by codeflash optimization agent

Reproduce the benchmark locally

# Verify black is in the import chain on main:
git checkout main
uv run python -X importtime -c 'import typeagent' 2>&1 | grep black
# Expected: multiple black.* lines (black.nodes, black.mode, pathspec, etc.)

# Verify black is deferred on this branch:
git checkout perf/defer-black
uv run python -X importtime -c 'import typeagent' 2>&1 | grep black
# Expected: no output (black no longer imported)

# A/B benchmark (requires hyperfine: https://github.com/sharkdp/hyperfine):
hyperfine --warmup 5 --min-runs 30 --shell=none \
  --prepare 'git checkout main && uv sync -q' \
  --command-name main \
  'uv run python -c "import typeagent"' \
  --prepare 'git checkout perf/defer-black && uv sync -q' \
  --command-name defer-black \
  'uv run python -c "import typeagent"'

Test plan

• 69 offline tests pass (uv run pytest)
• A/B benchmarked on dedicated non-burstable VM
• python -X importtime confirms black no longer in import chain