feat(harmonyos): refine adaptive chat and remote workflows

[wgqqqqq]

Summary

• Refine the HarmonyOS compact and wide conversation experience with adaptive navigation, floating sidebar controls, anchored menus, and stable in-place remote session selection.
• Add responsive native file and code preview flows, including file-reference projection, syntax highlighting, download states, and compact/wide placement policies.
• Complete system-following light/dark theme coverage and improve model, account, connection, settings, and session-action presentation.
• Rework compact remote session creation around the shared composer, including keyboard avoidance, workspace selection, model selection, and voice input.

Type and Areas

Type:

Feature / regression fix / UI/UX / docs / test

Areas:

HarmonyOS native mobile app only (src/apps/mobile/harmonyos)

Motivation / Impact

The HarmonyOS app had accumulated separate compact and wide interaction patterns, light-only visual assumptions, and page-transition behavior for selections that should update in place. This change aligns those workflows into one adaptive presentation model while keeping product and protocol behavior inside the HarmonyOS adapter boundary.

Users get a denser wide layout, a more coherent compact layout, theme-aware controls, clearer remote connection and retry states, native file previews, and a consistent composer across normal and remote session creation flows.

Verification

• source scripts/ohos-env.sh && "$HVIGORW" --mode module -p module=entry assembleHap --no-daemon - passed.
• pnpm run theme:color-audit:all - passed for Web UI, mobile web, installer, and CLI governance checks.
• Manual physical-device checks on HarmonyOS covered compact and wide navigation, sidebar/menu positioning, light/dark legibility, remote session selection/loading, file references, keyboard avoidance, and the remote-create workspace popup.

Reviewer Notes

• All 93 changed files are under src/apps/mobile/harmonyos/; there are no Rust, Web UI, installer, or other platform changes.
• The history is organized into 12 reviewable topic commits. Reviewing commit-by-commit is recommended because the complete diff includes the adaptive layout, file preview implementation, theme coverage, and follow-up interaction fixes.
• Design and implementation notes live alongside the HarmonyOS app under src/apps/mobile/harmonyos/docs/.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.