fix: escape pipe and backslash in Markdown/Notion tables (#16)

[cmeans-claude-dev]

Summary

• Add _escape_md_cell() helper that escapes \ to \\ then | to \|
• Apply escaping in _format_markdown() before width computation so column alignment is preserved
• Notion routes through _format_markdown, so it gets the fix automatically
• Add 7 tests covering pipe, double-pipe, backslash, backslash-pipe, leading/trailing pipe, and Notion equivalence

Part of the escaping series (#17, #18). Includes design spec for the full series.

Test plan

• uv run pytest tests/test_parser.py -v passes all 68 tests (7 new + 61 existing)
• Verify a cell containing | produces \| in markdown output
• Verify column alignment is correct with escaped values

Closes #16

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[cmeans]

QA Review — PR #44

Verdict: Zero findings. Ready for maintainer signoff.

Code review

_escape_md_cell() (parser.py:359): Escape order is correct — backslash first (\ → \\), then pipe (| → \|). Reversing would double-escape the backslash introduced by pipe escaping. ✓

Width computation (parser.py:373–377): Column widths computed from escaped values, not raw. This preserves table alignment when escaped characters change the visual width. Subtle and correct. ✓

Notion routing: format_table() dispatches notion to _format_markdown() (line 352), so Notion automatically inherits the fix. Confirmed by test_format_notion_escapes_pipe. ✓

Tests

Full suite: 233 passed, 0 failed, 0 deselected (226 base + 7 new).
Parser tests: 68 passed (61 existing + 7 new).

New tests (all PASS):

1. test_format_markdown_escapes_pipe_in_data — structural integrity via unescaped-pipe counting regex
2. test_format_markdown_escapes_pipe_in_header — pipe in header cell
3. test_format_markdown_escapes_double_pipe — || doesn't create extra columns
4. test_format_markdown_escapes_backslash — lone backslash escaped
5. test_format_markdown_escapes_backslash_pipe — \| → \\\| (escaped backslash + escaped pipe)
6. test_format_markdown_leading_trailing_pipe — edge case: leading/trailing pipes
7. test_format_notion_escapes_pipe — Notion equivalence confirmed

Tests verify structural integrity (unescaped pipe counts), specific escaped values, and edge cases. Covers the bug, not just the fix mechanics. ✓

Manual verification

| Cmd         | Desc   |
| ----------- | ------ |
| cat \| grep | filter |

Column alignment correct: 11-char separator matches cat \| grep width. \| appears in output, not a raw pipe. ✓

Other checks

• CHANGELOG: ### Fixed entry under [Unreleased]. Correct category, accurate description, Closes #16. ✓
• Design spec (docs/superpowers/specs/2026-04-11-table-formatter-escaping-design.md): Accurate coverage of the 3-PR series (#16, #17, #18). Correctly scopes #15 out (potential contributor). ✓
• CI: test (3.11/3.12/3.13), codecov/patch all SUCCESS. QA Gate pending. ✓

Merge coordination note (not a finding)

PR #44 and #45 both add ### Fixed to CHANGELOG but at different positions (before vs after ### Changed). Git will auto-merge both without conflict, creating two ### Fixed sections. Recommend: merge #44 first (it carries the design spec), then rebase #45 to consolidate its Fixed entry into the existing section. Adding merge-order labels to make this explicit.

Findings

None.

[cmeans]

Applying Ready for QA Signoff. 233/233 tests pass (7 new), manual verification confirms correct escaping and column alignment. Zero findings. Recommend merging this before #45 (both add CHANGELOG Fixed sections — second PR needs rebase to consolidate).

[cmeans]

LGTM