fix(cli): normalize numeric technical terms

[kkkano]

Problem

cw search currently assumes options.technicalTerms is always a string:

const technicalTerms = (options.technicalTerms || '')
  .split(',')

However, the CLI uses cac, and cac auto-casts numeric-looking option values to JavaScript numbers. Passing a year or other numeric token as --technical-terms therefore crashes before retrieval starts.

Repro

On current main, this crashes:

node dist/index.js search \
  --repo-path . \
  --information-request example \
  --technical-terms 2026

Observed error:

TypeError: (options.technicalTerms || "").split is not a function
  at .../dist/index.js:143:59
  at CAC.runMatchedCommand (.../node_modules/cac/dist/index.mjs:610:34)
  at CAC.parse (.../node_modules/cac/dist/index.mjs:537:12)

I also verified the underlying parser behavior directly:

2026       => 2026 number
0          => 0 number
001        => 1 number
2026,react => 2026,react string
react      => react string

So the bug is not downstream-specific: a direct CLI invocation with a numeric technical term can trigger it.

Fix

Normalize the CLI option at the CLI boundary before splitting:

const technicalTerms = String(options.technicalTerms ?? '')
  .split(',')
  .map((t) => t.trim())
  .filter(Boolean);

This keeps existing string behavior unchanged while making numeric values safe:

• 2026 becomes '2026'
• undefined / null become ''
• comma-separated strings continue to work as before

Validation

• pnpm build succeeds.
• After the fix, this no longer throws the .split is not a function error:

node dist/index.js search --repo-path . --information-request test --technical-terms 2026

The command reaches retrieval with normalized terms:

MCP codebase-retrieval 调用开始 {"technical_terms":["2026"]}

Mixed values also normalize correctly:

node dist/index.js search --repo-path . --information-request test --technical-terms 2026,react

MCP codebase-retrieval 调用开始 {"technical_terms":["2026","react"]}

In my local environment the retrieval later hit an unrelated embedding API batch-size error during indexing, but the CLI parsing crash covered by this PR is fixed and the command proceeds past the previous failure point.

Scope

This PR intentionally keeps the change minimal and only fixes the reported --technical-terms crash. Other string-like CLI options may deserve a separate audit because they are parsed by the same cac layer, but they are outside this small fix.