fix(extraction): tolerate whitespace in MyBatis close tags and fix qualified include refid

[fengshao1227]

Summary

Fixes two bugs in the MyBatis/iBatis mapper extractor (src/extraction/mybatis-extractor.ts), both reported and diagnosed in #1209:

• Whitespace in close tags — a close tag with trailing whitespace (</select >, legal XML) was missed by the statement regex. The non-greedy body overshot to the next real close tag, silently swallowing the statement in between. Fixed by adding \s* before > in the close-tag pattern.
• Qualified include refid — a fully-qualified <include refid="com.example.M.base"> had every dot replaced with ::, producing com::example::M::base which never matched the fragment node's qualifiedName (com.example.M::base). Fixed by splitting on the last dot only, consistent with qualifyStatement's own logic.

Also fixes the include-offset calculation to derive from the opening tag length rather than subtracting the close tag, so it stays correct when the close tag carries trailing whitespace.

Closes #1209

Test plan

• Added 4 new test cases in mybatis-extractor-robustness.test.ts:
  • Close tag with trailing space does not swallow the next statement
  • <include> still resolves after a spaced close tag
  • Cross-mapper refid with multi-dot namespace resolves correctly
  • Bare refid regression guard (same-namespace, no dots)
• All 21 existing + new tests pass (npx vitest run __tests__/mybatis-extractor-robustness.test.ts)