fix(ui): keep filter row alive during table rebuild so typing never loses focus (rant 2026-08-25T11:15:16)

[argszero]

Summary

Fix a regression from PR #146 (v0.7.18 server-side column filters): typing into a column-filter input on the transactions page lost focus after every keystroke, making it impossible to type a full word (e.g. "sh" — after "s" the input loses focus).

Root cause: input debounce callback → renderTransactions detects the filter-signature change → loadTransactions() async fetch → after fetch returns, renderTransactions → buildDataTable executes container.innerHTML = html (full table rebuild) → the old filter input is destroyed, focus lost. The focus-restore code ran after the render that triggered the fetch, not after the DOM rebuild that follows the fetch return.

Fix (host-confirmed option B): the header filter row is separated from the full-table rebuild — buildDataTable now renders the thead (sort buttons + filter row) only once per container and rebuilds only the tbody + pager on every render, so the filter input DOM is never destroyed and focus is naturally preserved.

Related Issue

Rant 2026-08-25T11:15:16 (verbatim):

交易记录页列筛选输入框：每输入一个字母就触发刷新并失去焦点，无法完整输入一个单词（如想输入 "sh"，输入 "s" 后焦点丢失）。v0.7.18 服务端列筛选改造（PR #146）后的回归。

【修复方案（宿主确认：只做 B）】重建表格时不动表头筛选行——把筛选输入行从整表重建中分离（独立容器/独立 innerHTML），只重建数据行与分页器；输入框 DOM 永不销毁，焦点天然保留。

Changes

• ui/js/app.js:
  • tableTheadHtml() — thead (sort buttons + filter row) rendered once, only when the container has no <table> yet; input values seeded from state.filters on first render, afterwards the inputs are the DOM source of truth
  • tableBodyHtml() — data rows, rebuilt on every render
  • buildDataTable() — rebuilds only tbody + pager; container-level one-time event delegation (sort / filter input / pager / page-size / IME) reads the latest config via container._dt, so events survive rebuilds and are never lost after the first keystroke
  • IME composition tracking (compositionstart/compositionend + focusout safety): no table rebuild and no setSelectionRange while composing; a refresh is debounced after compositionend — Chinese IME composition is not interrupted
  • focus restore kept only as a fallback when the input is not already focused (no cursor jumps while typing)
• ui/index.html: cache-bust bumped to 20260825-2

Tests

• node --check ui/js/app.js — OK
• cargo test — 147/147 pass
• Manual reasoning of the full event flow (debounce → filter-sig reload → tbody-only rebuild → focus preserved)

Checklist

• Conventional commit message, branch fix/<description>
• PR based on main (default branch)
• No behavior change for tables without filter columns (thead persistence is transparent, events delegated)