docs(refid): add ID pattern catalog

[sthanikan2000]

Summary

• Add refid/docs/PATTERNS.md, cataloging the ID shapes producible from refid's segment grammar (literal, list, date, sequence) and the sequence reset-cadence dimensions, each backed by a runnable example Config.
• Link the new doc from refid/README.md right after the Scope Key Placeholders section.

Test plan

• go test -race ./... passed (via pre-push hook)
• Docs-only change; no code paths affected

[coderabbitai]

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[ginaxu1]

non-blocking nits:

1. Example IDs use 000042. 1st call is 000001. Same convention as the existing README; a one-liner would make that obvious
2. Line-number links will rot. registry.go:173–187 is accurate today; a later edit will silently point at the wrong function. Symbol names are more durable.
   3.*Section 2 slightly overstates "placeholders only" Isolation is the fully resolved scope-key string. P8’s :primary / :secondary suffixes also split counters
3. Shared scopeKey on two sequences does more than "share one counter": one Generate consumes two increments (A-000001-000002). Worth one sentence in P8.
4. Visible ID and reset cadence are independent. You can put a daily date in the ID and a never-resetting sequence (or the reverse). The catalog couples them in examples but never says that mismatch is legal and easy to misconfigure.
5. "Reset" is a new scope_key row, not truncation of the old counter. Matches existing README language, so not a new inaccuracy