fix: normalize spaces in workflow variable inputs

[Iams4kura]

What

• Normalize browser-generated non-breaking spaces when serializing workflow variable inputs.
• Add a regression test covering an MCP SQL parameter with an inserted variable followed by U+00A0.

Why

VarInput copied contentEditable text nodes verbatim. Browsers can represent the space next to a non-editable variable badge as U+00A0, so the saved SQL reached the MCP database with an invalid separator and failed to parse.

How

Replace U+00A0 with an ordinary U+0020 while traversing text nodes. Variable badges, line breaks, and all other input remain on the existing serialization path.

Test

• 本地测试通过
• 114 测试服务器验证通过
• Regression before: npm test -- --run src/pages/BuildPage/flow/FlowNode/component/VarInput.test.tsx exited 1 with U+00A0 preserved.
• Regression after: the same command exited 0.
• Smoke + affected tests: npm test -- --run src/test/smoke.test.ts src/pages/BuildPage/flow/FlowNode/component/VarInput.test.tsx
• Production build: npm run build
• Architecture guard: bash scripts/arch-guard.sh
• Staged diff check: git diff --cached --check
• Full platform suite has 14 unrelated baseline failures both before and after this patch; the patched run adds this regression as one additional passing test.

Related

• Issue/ticket: Fixes MCP工具节点中写SQL 时，引入变量会存在不间断空格，导致SQL语法错误 #2155

Scope

• 2 files changed, +58 / -1 lines