[Elon-Jiang]

Description

Memory consolidation can silently remove a valid topic link. For example,
consolidate(["- [API reference](api.md)", "- [API reference](api.md.v2.md)"])
currently keeps only the second pointer: the serialized identity of the first
is a prefix of the second and is treated as redundant prose. The real
consolidate_pointer_index() writer can persist that loss to MEMORY.md.
A literal | split between title and target can also make distinct pointers
share one serialized key.

Use a (title, target) tuple for pointer identity and apply prefix subsumption
only to prose keys. Existing case normalization, repeated-link/hook merging,
first-seen ordering, and index capacity limits remain unchanged.

Related Issues

Source-discovered regression in the pointer-index feature introduced in #233.
No overlapping open PR was found during the current-main check.

Changes Made

• Represent topic identities structurally so distinct links do not collide.
• Keep prose prefix deduplication separate from topic-pointer deduplication.
• Add five regressions: both orders of prefix/delimiter examples and a real
  index rewrite that preserves both topic links and their readable contents.
• Add English and Chinese changelog entries.

Checklist

• Changes tested locally: 5 new tests fail on current main, 32 existing
  memory-layer tests pass; all 74 memory/compaction/autodream tests pass with
  the fix.
• Full Python suite on Python 3.12.14 / macOS: 3063 passed, 12 skipped,
  1 failed. The sole failure,
  test_ctrl_c_clears_a_draft_before_it_interrupts, also fails on unchanged
  upstream e09d3c1 with the same locked dependencies. No test was excluded.
• Required pre-commit run --all-files: all hooks pass (Ruff lint/format,
  whitespace/requirements checks, and actionlint).
• Desktop/Web lint, 51 test files / 355 tests, typecheck, protocol check,
  and Web build pass.
• Maintainer review.
• Documentation updated through changelog entries.
• Unit tests added.

Additional Notes

AI-assisted contribution. The unrelated TUI baseline failure is reported
above rather than presented as a passing full suite. No runtime dependencies
or provider calls are added.