fix(workflows): cap gate show_file line width, not just its line count

[jawwad-ali]

Problem

GateStep._read_show_file bounds the number of lines:

if len(lines) >= GateStep.MAX_SHOW_FILE_LINES:
    truncated = True
    break

but nothing bounds a single line's length. A file with no newlines — minified JSON, a lockfile, a base64 blob, all plausible review material to put in front of an approver — is one line of arbitrary size, so the cap never triggers and the whole file floods the prompt. That is exactly the outcome MAX_SHOW_FILE_LINES exists to prevent.

Reproduction on current main (c173bf1)

many short lines : returned 201 lines, total chars=1323    (cap=200)
one long line    : returned   1 lines, total chars=400008  <-- unbounded

The 5,000-line file is correctly clipped to 1,323 characters. The single-line 400 KB file passes through whole.

The content is also rendered inside the gate box one character at a time by _prompt, so the operator's terminal is buried and the choice prompt is pushed far off screen.

Fix

Add a per-line cap alongside the line cap, with a notice in the same style as the existing one:

MAX_SHOW_FILE_LINE_CHARS = 500
...
if len(clean) > GateStep.MAX_SHOW_FILE_LINE_CHARS:
    clean = clean[:GateStep.MAX_SHOW_FILE_LINE_CHARS] + "… (line truncated at 500 characters)"

After the fix:

many short lines : 201 lines, 1323 chars (unchanged)
one long line    :   1 lines,  536 chars
short file       : ['hello', 'world']    (untouched)

Verification

• Fail-before / pass-after: 1 new-vs-baseline failure with the source reverted to upstream/main → 49 passed with the fix.
• A companion test asserts short lines are still rendered verbatim with no notice, so the cap cannot start mangling ordinary files.
• The existing test_read_show_file_truncates_large_file, test_read_show_file_strips_control_chars and test_read_show_file_empty all use short lines and are unaffected — they pass unchanged.
• uvx ruff@0.15.0 check src tests → clean

Behaviour change, disclosed: a show_file line longer than 500 characters is now rendered truncated with a notice instead of in full. That is the intent; no existing test exercises such a line.

Note on overlap: this touches steps/gate/__init__.py, as does my #4529, but a different function (_read_show_file vs _prompt). They should merge independently — happy to rebase whichever lands second.

---

Written with assistance from Claude Code. Bug found, reproduced, and verified by me on current main.

🤖 Generated with Claude Code

[Copilot]

🟢 Approval recommended

The focused fix correctly addresses the prompt-flooding regression with appropriate test coverage.

Pull request overview

Bounds gate show_file output by truncating oversized lines while preserving ordinary content.

Changes:

• Adds a 500-character per-line cap with a truncation notice.
• Adds regression and unchanged-content tests.

File summaries

File	Description
src/specify_cli/workflows/steps/gate/__init__.py	Implements per-line truncation.
tests/test_workflows.py	Tests long-line truncation and short-line preservation.

Review details

• Files reviewed: 2/2 changed files
• Comments generated: 0
• Review effort level: Balanced

---

💡 Configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[mnriem]

Please resolve conflicts