[PATCH v3 0/5] docs(l10n): AI agent instructions and workflow improvements

## Changes since v2

- CI: Fix trailing spaces that caused check-whitespace to fail.
- Size: Trim po/AGENTS.md by removing unnecessary examples and compressing
  wording so the file stays smaller and easier to follow.
- GETTEXT JSON: Use a single `msgstr` array for all translations instead
  of separate `msgstr` (string) and `msgstr_plural` (array). One element
  means singular; multiple elements mean plural forms in order. This reduces
  redundancy and model errors.
- Workflow: Rename the final step of translation workflow to "Only after
  loop exits" so agents do not jump from the merge step to the final step
  before the loop has exited. Simplify the review flow by using one pending
  file for entries awaiting review instead of multiple review-input-<N>.json
  files and file-selection logic.

## Introduction

This series introduces AI agent instructions for Git localization (l10n) workflows to help localization contributors quickly complete drafts and use AI to check translation quality. The changes focus on:

1. Separating agent-specific documentation into po/AGENTS.md for
   targeted optimization of AI-assisted workflows
2. Providing step-by-step instructions for update-pot, update-po,
   translation, and review tasks
3. Simplifying location filtering for PO file commits via .gitattributes

AI-assisted translation is optional; many successful l10n teams work well without it. When used, AI output serves as reference only—human contributors must review and approve before submission.

## Performance summary

Benchmarks use the Qwen model via git-po-helper. The improvements reduce API costs and make agent workflows more efficient while maintaining human oversight of translation quality.

| Task        | Before              | After                    | Improvement                           |
|-------------|---------------------|--------------------------|---------------------------------------|
| update-pot  | 17 turns, 34s       | 3 turns, 8s (range 3–3)  | -82% turns, -76% time                 |
| update-po   | 22 turns, 38s       | 4 turns, 9s (3–9, 7–14s) | -82% turns, -76% time                 |
| translate   | 86 turns, ~21m      | 56 turns, ~19m           | -35% turns (git-po-helper JSON batch) |
| review      | N/A                 | 22 turns (63 entries)    |                                       |

## Testing

All changes have been evaluated with the qwen model via git-po-helper agent-test and agent-run. The po/AGENTS.md instructions are designed to work with coding tools that support file references (e.g., "Translate po/zh_CN.po by referring to @po/AGENTS.md").

## Changes

Jiang Xin (5):
  l10n: add .gitattributes to simplify location filtering
  docs(l10n): add AGENTS.md with optimized update-pot instructions
  docs(l10n): add AI agent instructions for updating po/XX.po files
  docs(l10n): add AI agent instructions for translating PO files
  docs(l10n): add AI agent instructions to review translations

 po/.gitattributes |  36 ++
 po/AGENTS.md      | 872 ++++++++++++++++++++++++++++++++++++++++++++++
 po/README.md      |  70 ++--
 3 files changed, 946 insertions(+), 32 deletions(-)
 create mode 100644 po/.gitattributes
 create mode 100644 po/AGENTS.md