docs(proxy): correct --code-aware default to disabled

[Parideboy]

Description

The wiki proxy page (wiki/proxy.md, which feeds the published docs site) claimed --code-aware defaults to true. The CLI deliberately defaults it to disabled: headroom/cli/proxy.py resolves the paired flag to off unless --code-aware is passed or HEADROOM_CODE_AWARE_ENABLED is truthy, and the Click help text plus docs/content/docs/proxy.mdx and wiki/cli.md already document it as disabled. This PR aligns the one remaining stale table row and collapses the self-contradictory separate --no-code-aware row into a single paired-flag entry, matching the style used in docs/content/docs/proxy.mdx.

Fixes #1700

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Performance improvement
• Code refactoring (no functional changes)

Changes Made

• wiki/proxy.md: replaced the two flag-table rows claiming --code-aware default true / --no-code-aware default false with one --code-aware / --no-code-aware row documenting the actual default (disabled), the headroom-ai[code] requirement, and the HEADROOM_CODE_AWARE_ENABLED=1 env opt-in.

Testing

• Unit tests pass (pytest)
• Linting passes (ruff check .)
• Type checking passes (mypy headroom)
• New tests added for new functionality
• Manual testing performed

Test Output

$ python -c "
from click.testing import CliRunner
from headroom.cli.proxy import proxy
r = CliRunner().invoke(proxy, ['--help'])
print([l.strip() for l in r.output.splitlines() if 'code-aware' in l][0])
"
--code-aware / --no-code-aware  Enable/disable AST-based code compression.

$ grep -n "code-aware" wiki/proxy.md
77:| `--code-aware` / `--no-code-aware` | disabled | Enable or disable AST-based code compression. Requires `headroom-ai[code]` (env: HEADROOM_CODE_AWARE_ENABLED=1 to enable) |

Real Behavior Proof

• Environment: Windows 11, local checkout at upstream/main (9fbd47b), Python 3.13.
• Exact command / steps: headroom proxy --help (via Click test runner) to confirm the CLI help says "Default: disabled"; inspected headroom/cli/proxy.py flag resolution (explicit flag → HEADROOM_CODE_AWARE_ENABLED → off); grep -rn "code.aware" wiki/ docs/ to find every doc stating a default.
• Observed result: CLI default is disabled; docs/content/docs/proxy.mdx:61 and wiki/cli.md:255-256 already say disabled/off; only wiki/proxy.md:77-78 claimed true. After the change the table matches actual behavior.
• Not tested: rendered docs-site build (content-only table edit).

Review Readiness

• I have performed a self-review
• This PR is ready for human review

[github-actions]

PR governance

This PR follows the template and is marked ready for human review.

[JerrettDavis]

Docs review looks good. The wiki table now matches the CLI's paired --code-aware / --no-code-aware behavior and the existing docs that describe code-aware compression as disabled unless explicitly enabled.