REMOVED and RENAMED entries written with * or + bullets are silently ignored #1799

The REMOVED bullet form and the RENAMED FROM:/TO: form only recognise the
- list marker. CommonMark also allows * and +, which render identically.
An entry written with either of those matches nothing, so the removal or rename
silently never happens — with no error, no warning, and a success exit code.

Reproduction

Main spec has Invoice Generation and Late Fees. Delta:

## REMOVED Requirements

* `### Requirement: Late Fees`

## ADDED Requirements
### Requirement: Dunning Notices
The system SHALL send a dunning notice when an invoice is 7 days overdue.

#### Scenario: Invoice overdue
- **WHEN** an invoice is 7 days overdue
- **THEN** a dunning notice is sent

openspec validate chg --json   # "valid": true, "issues": []
openspec archive chg --yes     # exit 0, "Totals: + 1, ~ 0, - 0, → 0"

Expected

Late Fees removed, or an error saying the REMOVED entry was not understood.

Actual

- 0 removals. Late Fees is still in openspec/specs/billing/spec.md, and the
change has been archived as complete.

Impact

The main spec keeps a requirement that was supposed to be deleted, so it now
misdescribes the system, and the delta that would explain the discrepancy has
moved to changes/archive/. * is valid CommonMark, is emitted by several
formatters, and is already accepted by this project's own task-line parser.

Mitigating: the documented example in skills/openspec-sync-specs/SKILL.md uses
-, so an author copying it directly is not affected.

Environment

• OpenSpec 1.12.0 (reproduced on the published npm package and on a build of
  main @ e062b95)
• Node v22.23.2, Linux