[laozidabo]

What and why

/diff returns English feedback and a pager title even when another UI language is selected. Route its nine user-facing messages through the existing presentation facet and typed diagnostics mapping, with translations in all 15 complete locale packs.

For example, with Simplified Chinese selected, No changes since session start becomes 会话开始以来没有变更. English output, error/action behavior, filenames and raw Git payloads stay unchanged.

Issue

Refs #7071 (partial)

This PR addresses /diff. /undo and the other remaining surfaces are still tracked in #7071.

How I tested it

On Linux, using the installed toolchain and linker:

cargo fmt --all -- --check
git diff --check HEAD^
CARGO_BUILD_JOBS=1 CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=/usr/bin/cc scripts/dev-cargo.sh test -p codewhale-commands --lib --locked
CARGO_BUILD_JOBS=1 CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=/usr/bin/cc scripts/dev-cargo.sh test -p codewhale-localization --lib --locked
CARGO_BUILD_JOBS=1 CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=/usr/bin/cc scripts/dev-cargo.sh clippy -p codewhale-commands --lib --locked --no-deps -- -D warnings -A clippy::uninlined_format_args -A clippy::too_many_arguments -A clippy::unnecessary_map_or
CARGO_BUILD_JOBS=1 CARGO_TARGET_X86_64_UNKNOWN_LINUX_GNU_LINKER=/usr/bin/cc scripts/dev-cargo.sh clippy -p codewhale-localization --lib --locked --no-deps -- -D warnings -A clippy::uninlined_format_args -A clippy::too_many_arguments -A clippy::unnecessary_map_or

Formatting, whitespace checks, 28 commands tests, 54 localization tests, and the focused Clippy checks passed. The existing command fixture now supplies English presentation, and its capability expectation includes PRESENTATION.

A committed regression case also runs the actual diff handler against the Simplified Chinese catalog and verifies translated interpolation, the stat header, pager title and unchanged raw patch. It fails against the original English-only handler and passes with this fix. The changed command/localization crates additionally pass Clippy with --all-targets --all-features --no-deps.

A separate local reproduction harness (not included in this commit) invokes the actual registered handlers and real catalog/mapping/interpolation. It reproduces the Chinese failure against the original handler, then checks the updated handler across all complete locale packs. Its output is:

BASELINE: 8/8 Chinese expectations fail as reproduced; sample "No changes since session start"
FIXED Chinese sample: 会话开始以来没有变更
PASS: 120 localized outcomes (8 × 15), 8 English parity comparisons, 135 catalog/mapping contracts, 30 opaque-payload cases; action/error/patch preserved

Clippy including dependencies encountered the existing clippy::large_enum_variant warning in unchanged crates/protocol/src/op.rs:209. The focused checks above exclude dependencies and use the project's documented allowances.

The full TUI/workspace build, real host Git collection and interactive terminal/pager rendering were not exercised locally. No UI screenshot or recording was captured; the reproduction verifies returned messages and pager metadata, not visual rendering.

Checklist

• One focused change, started from current main (no need to rebase when main moves)
• cargo fmt --all passes, and tests cover new or changed behavior
• If this adds or changes a user-facing feature, I updated its docs and its row in docs/features.toml (cargo test -p codewhale-tui --test feature_registry checks it)

The docs/feature-registry item is not applicable: this fixes translation of the existing /diff feature.

AI disclosure: AI assistance was used for investigation, implementation, translation, testing and review on behalf of @laozidabo. The account owner has not personally written or technically reviewed it.

[claude]

Claude Code Review

This pull request is from a fork — automated review is disabled. A repository maintainer can comment @claude review to run a one-time review.

[laozidabo]

CI triage note for reviewers:

The current red checks do not appear to be caused by this PR's /diff changes:

• Version drift reports missing release-note receipts for already-merged feature commit 4cf2d2c (In the Linux version's multiline mode, messages cannot be sent with Shift+Enter. #7093/fix(tui): resolve the state root before opening session-side state #7097), not for the two commits in this PR.
• The full-workspace lint leg is failing on unrelated PRs as well (fix(tui): keep the workspace folder in view when /context shortens its path #7103, fix(catalog): read the token limits a live model listing states #7105, chore(tui): re-apply rustfmt to mcp.rs #7106 and fix(installer): avoid downloading identical codew asset twice #7107). Locally, the changed command/localization packages pass the PR's Clippy flags with --all-targets --all-features --no-deps; a dependency-inclusive run reaches the pre-existing clippy::large_enum_variant in unchanged crates/protocol/src/op.rs.
• The Linux workspace, Windows compile and Windows extension-host failures also reproduce on unrelated PRs from the same main window (Linux on fix(tui): keep the workspace folder in view when /context shortens its path #7103/chore(tui): re-apply rustfmt to mcp.rs #7106; Windows and extension-host also on fix(catalog): read the token limits a live model listing states #7105/fix(installer): avoid downloading identical codew asset twice #7107). The detailed hosted logs require sign-in, so I have not attributed their exact failing steps beyond that cross-PR signal.

I have left those unrelated protocol, extension-host and release-note areas untouched to keep this PR scoped to /diff localization. The PR-owned evidence remains: formatting, locale parity, 28 commands tests, 54 localization tests, focused Clippy, and the committed Simplified Chinese regression case that fails against the original handler and passes with this fix.

Once main's shared failures are repaired, a rerun should provide a cleaner signal for this PR.