Amend grammar: bare-token clauses at the end of a provision

The audit over 8 amending acts (7,421 instructions EN+FR) ranked
add-provision as the largest unhandled mass (23.3%), and traced its
dominant refusal to the bare-conjunction-token clause: striking
out/adding a quoted token at the end of a paragraph. Worse, the
strike variant silently compiled UNSCOPED (whole-provision
strike_text with no end anchor) - a best-effort guess where the
calculus promises typed refusals.

- strike/substitute clauses parse the 'at the end of <provision>'
  tail: child-scoped target, last-occurrence anchor, whole-word match
- new append_text op: 'adding X at the end of <provision>'; the
  applier owns list re-punctuation (terminal '.' becomes '; X',
  terminal ';' gains ' X', anything else is a typed refusal)
- gold: SC 2021, c. 24, s. 1(1) round-trips onto today's CLC
  s. 164(1) consolidation exactly (normalized), 23/23 tests

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018bhP89cYSdEEjHNPnxacns