fix(pipeline/template): preserve commas in replace() filter replacement value

[Chen17-sq]

Problem

The replace(old, new) pipeline template filter truncates any replacement value that contains a comma. For example:

item.x | replace('a', 'x,y')   // with item.x === 'a'

returns 'x' instead of the expected 'x,y'.

Root cause

src/pipeline/template.ts:103 (pre-fix) split the raw filter arguments on every comma:

const parts = rawArgs?.split(',').map(s => s.trim().replace(/^['"]|['"]$/g, '')) ?? [];
return parts.length >= 2 ? value.replaceAll(parts[0], parts[1]) : value;

replace('a', 'x,y') has rawArgs === "'a', 'x,y'", which split(',') turns into ["'a'", " 'x", "y'"]. Only parts[0] (a) and parts[1] (x) are used, so the replacement is silently truncated at the first comma in the value.

Fix

Split on the first comma only, treating everything after it as the replacement value:

case 'replace': {
  if (typeof value !== 'string') return value;
  if (rawArgs == null) return value;
  const ci = rawArgs.indexOf(',');
  if (ci === -1) return value;
  const strip = (s: string) => s.trim().replace(/^['"]|['"]$/g, '');
  const oldVal = strip(rawArgs.slice(0, ci));
  const newVal = strip(rawArgs.slice(ci + 1));
  return value.replaceAll(oldVal, newVal);
}

This makes replacement values containing commas work while keeping existing behavior for simple args (single-comma usage, non-string passthrough, single-arg no-op). Quote-stripping and replaceAll semantics are unchanged.

Tests

Added five co-located unit tests in src/pipeline/template.test.ts (the evalExpr filter block had no prior replace coverage, so there is zero regression risk):

• control: replace('foo','bar') on 'foo baz' -> 'bar baz'
• the bug: replace('a','x,y') on 'a' -> 'x,y'
• multiple, unquoted: replace(' ','_') on 'a b c' -> 'a_b_c'
• non-string passthrough unchanged (42 -> 42)
• single-arg replace('a') returns the value unchanged

npx vitest run src/pipeline/template.test.ts: 57 passing (52 baseline + 5 new). tsc --noEmit clean. The existing join(,) test is on a separate code path and is unaffected.

Scope

Single-concern: this PR fixes only the replace-filter comma splitting. Two related items are deliberately left out to keep the change surgical:

• A literal comma needle (replace(',', ';')) remains unsupported by design — the comma is the argument separator. This fix only guarantees the replacement value may contain commas.
• The separate single-|-in-filter-args concern (e.g. join(|), handled by the pipe tokenizer at template.ts:43) is out of scope; addressing it would require a paren-aware change to the hot-path tokenizer and turn this into a two-concern parser PR. It can be a follow-up if there is demand.

A full quoted-arg parser was intentionally avoided to keep the diff small and low-risk.