test(adcp): docstring/env-var consistency test

[bokelley]

Closes #424

Adds tests/test_docstring_consistency.py. The test AST-parses all public method, class, and module docstrings in src/adcp/, extracts env-var names documented as active, and asserts each one is backed by a real os.environ read in the source tree. CI fails on drift — the original trigger was client.py:381-388 claiming PYTHON_ENV / ENV / ENVIRONMENT were honored when only ADCP_ENV was.

Detection logic:

• Pattern A — VARNAME=value inside RST double-backtick literals (e.g. ADCP_VALIDATION_MODE=strict|warn|off ). Direct signal that a var is documented as settable.
• Pattern B — SCREAMING_CASE_WITH_UNDERSCORE inside a backtick span, with an env-var context keyword (environ, env var, environment variable, flips) in the ±1-line window. The sliding window catches ADCP_ENV on one line when flips … appears on the next. Restricted to backtick-wrapped tokens; overrides excluded as standalone keyword to prevent OOP-override false positives.
• Exclusion — lines containing deliberately or not honored are skipped.

What was tested:

• pytest tests/test_docstring_consistency.py — 1 passed
• mypy tests/test_docstring_consistency.py — no issues
• ruff check tests/test_docstring_consistency.py — all checks passed

Pre-PR review:

• code-reviewer: approved — no blockers; nits surfaced (raw-text scan limitation, PORT coverage gap, SyntaxError comment) all documented in module docstring or addressed in the follow-up commit
• dx-expert: approved after fixes — initial blockers (greedy regex suffix match, missing ±1 window, bare overrides keyword, bare ignored? exclusion) all resolved in the second commit

Known limitations (documented in module docstring):

• Single-token env vars without underscores (PORT) are invisible to both patterns
• _env_vars_in_use() scans raw text; a docstring example embedding a fictional os.environ["FAKE_VAR"] would suppress that name in the in-use set
• ast.walk collects public methods inside private classes (over-approximation)

Triage-managed PR. This bot does not currently iterate on
review comments or PR conversation threads (only on the source
issue). To unblock:

• Push fixup commits directly: gh pr checkout <num> →
  fix → push.
• Or re-trigger: comment /triage execute on the source
  issue.

See adcp#3121
for context.

Session: https://claude.ai/code/${CLAUDE_CODE_REMOTE_SESSION_ID}

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