feat: add edit, tags, and stats commands (client parity)

[icco]

Summary

• Adds etu edit (alias e): pick an entry, edit its content in a pre-filled form, save via UpdateNote (tags untouched); prints "No changes." when content is unchanged
• Adds etu tags (alias t): plain, pipeable name (count) list sorted by count desc, name asc
• Adds etu stats: Blips / Tags / Words written, with --global for community stats (empty UserId in GetStatsRequest)
• Wires TagsServiceClient and StatsServiceClient into the client package alongside the existing service clients
• Documents the new commands in the README and adds a CLAUDE.md

This closes the CLI's feature-parity gap with the web client (which already exposes edit, tags, and stats).

Test plan

• go build ./..., go vet ./..., gofmt -l . clean
• go test ./... passes (new table tests for tag conversion/sorting and stats formatting)
• golangci-lint run ./... — 0 issues

[Copilot]

Pull request overview

Adds CLI feature parity with the web client by introducing etu edit, etu tags, and etu stats, plus the necessary gRPC client wiring and documentation updates.

Changes:

• Added new Cobra commands: edit (TUI edit flow), tags (pipeable tag counts), and stats (personal + optional community stats via --global).
• Extended the client package to wire TagsServiceClient / StatsServiceClient and expose ListTags, GetStats, and UpdatePost.
• Added unit tests for tag conversion/formatting and stats formatting; updated README and added CLAUDE.md.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tags.go	Adds etu tags command and deterministic sorting/formatting helper.
tags_test.go	Tests formatTags output and ordering rules.
stats.go	Adds etu stats command and formatting helper with optional community block.
stats_test.go	Tests stats rendering for personal-only, community, and zero values.
edit.go	Adds etu edit command: select entry, load full content, edit via huh, update via client.
main.go	Registers new commands and adds stats --global flag.
README.md	Documents the new commands in the usage list.
client/grpc.go	Wires Tags/Stats service clients and adds proto→client tag conversion helper.
client/grpc_test.go	Tests protoTagsToTags conversion behavior.
client/client.go	Adds UpdatePost, ListTags, GetStats, and new Tag/Stats types.
CLAUDE.md	Adds contributor-facing repo/build/test/architecture notes.
docs/superpowers/plans/2026-06-12-cli-parity.md	Adds an implementation plan document for CLI parity work.

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