feat(cli): add sprout notes for NIP-23 long-form notes

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What

Adds sprout notes — a command group for editable NIP-23 long-form notes (kind:30023). This is our team knowledge base: write a skill once as an editable note, reference it by name from agent memory instead of re-deriving it.

Surface (v1)

verb	behavior
notes set --name <slug> [--title T] [--summary S] [--tag t]... [--clear-tags] --content -	Idempotent upsert keyed by (kind:30023, me, d=slug). Read-before-write preserves published_at on edits and carries title/summary/tags when omitted; ""/--clear-tags clears. --title required on first publish. Prints durable refs (event id, naddr, coordinate, slug).
notes get (--naddr <naddr> | --name <slug> [--author <ref>]) [--content-only]	Exact by coordinate; cross-author #d lookup by name. >1 hit → candidates + non-zero exit. Never guesses.
notes ls [--author <ref>] [--tag t] [--limit N]	Own notes by default; --author all across the team. Bounded (default 50, cap 200).

notes rm is intentionally deferred: the relay's NIP-09 a-tag deletion is a no-op for 30023 today (#714, fix in #716). rm lands once that's authoritative, so set/get/rm all operate on the same coordinate identity rather than shipping an event-id-based delete next to coordinate-based set.

Design

• naddr is the canonical reference; --name + --author is the human form. Memory pointers store both.
• Standard NIP-23 tags only (d/title/summary/t/published_at); global, no h-tag.
• Pure, relay-free units: carry-forward logic (build_set_event) and tag parsing (NoteSnapshot::from_event) are fully unit-tested; e2e_long_form gains a set-twice-preserves-published_at round-trip.

Testing

cargo test -p sprout-cli --lib 98/98 · clippy --all-targets -D warnings clean · fmt --check clean · e2e_long_form compiles (relay-gated like its siblings).

Co-authored by Dawn (scaffold + helpers), Max (get/ls), Quinn (set). Closes the CLI half of the long-form notes effort; #716 is the independent relay-side companion.

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Superseded by #719 (combined CLI + relay a-tag fix per Tyler).