notations: add IDs and cross-references appendix

[transitrix]

Summary

• New notations/IDS_AND_REFERENCES.md defines the canonical ID grammar <TYPE>-[<middle segment(s)>-]<INTEGER>, documents the CAPABILITY V/H exception, enumerates the complete TYPE registry (element types + document-level prefixes), states uniqueness scope per TYPE, the cross-reference pattern, and a migration checklist for files still using old forms.
• Eight specs (03, 04, 05, 06, 07, 09, 10, 11) gain a one-line link to the appendix in their References section.

Closes vkgeorgia/strategy#13.

Scope guard

Per the issue refinement, this PR produces only the new appendix file and adds a cross-link from each spec that references IDs. No other spec content changes; no example rewrites; no audit items.

Which specs are linked vs not

• Linked (8): 03-fga, 04-goals, 05-capability-map, 06-process-map, 07-activities, 09-products, 10-applications, 11-scenarios.
• Not linked, by design (3):
  • 01-bpmn uses only file-local labels (POOL, TASK, GW…), explicitly noted as out of scope in the appendix §3.3.
  • 02-fgca on main has no schema and therefore no IDs yet; it will gain the link as part of transitrix/methodology#7 which introduces its schema.
  • 08-blocks uses ASCII art with no element IDs.

Migration

The appendix carries a migration checklist documenting which existing files still use old ID forms (ACT-, CHG-, FAC-, CAP-, SCN-, integer-only IDs, zero-padded sequences). The migration itself is out of scope — per-notation follow-ups will do it gradually. The integer-IDs row in the FGCA example is already in flight via #7.

Test plan

• notations/IDS_AND_REFERENCES.md exists with all seven sections (Grammar, Capability exception, TYPE registry, Uniqueness scope, Cross-references, Migration checklist, References).
• Every listed spec contains exactly one new link to the appendix in its References section.
• No links to the private vkgeorgia/strategy repo in any shipped file.
• Existing References-section content untouched apart from the inserted line.

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