feat: replace bundled skills with single using-skillshub default

[EYH0602]

Summary

• Remove 13 previously bundled skills from skills/ (analyze-ci, docs-review, docstring, fuzzing, github-actions-templates, paper-polish, python-packaging, read-repo-references, senior-data-scientist, temporal-python-testing, testing-python, uv-package-manager, write-unit-tests). Default tap is intentionally being curated down to a single focused skill.
• Add a new bundled skill, using-skillshub, that teaches AI coding agents how to drive the skillshub CLI: tap → install → link mental model, a command decision table, common workflows, and SKILL.md authoring guidance. Bundles cli-reference.md and architecture.md as references so it stays self-contained after skillshub install.
• Update README, CLAUDE.md, AGENTS.md, and src/cli.rs doc-comment examples so they reference EYH0602/skillshub/using-skillshub (which now exists in this tap) instead of code-reviewer (which never did). Copy-pasted examples now work against the default tap out of the box.
• CHANGELOG records additions, removals, and example updates.

Test plan

• cargo build passes
• cargo test passes (43 tests across both integration suites)
• cargo run -- install EYH0602/skillshub/using-skillshub resolves and installs against this branch
• cargo run -- info EYH0602/skillshub/using-skillshub shows the new skill metadata
• skillshub link creates ~/.claude/skills/using-skillshub symlink after install
• Bundled references/cli-reference.md and references/architecture.md ride along with the install
• Spot-check README's Quick Start examples actually install something from the default tap

[fenfenai]

Review summary

Reviewed the substantive changes (the new using-skillshub skill, bundled references, src/cli.rs doc-comment substitutions, and the README/CLAUDE.md/AGENTS.md/CHANGELOG updates). Bulk skill removals were not reviewed line-by-line — they're intentional scope per the plan.

The load-bearing factual claims in SKILL.md were spot-checked against src/registry/skill.rs, src/registry/git.rs, src/agent.rs, src/cli.rs, and src/commands/clean.rs and all hold up: the @commit rejection, the 17-agent enumeration (Kiro→steering, the rest→skills), the three-location mental model, skillshub clean all semantics, and the gist-vs-tap split are all accurate.

Two inline findings + one PR-description-level note below.

Important (confidence 90-100)

1. skills/using-skillshub/references/cli-reference.md:13 (95) — internal contradiction with SKILL.md and the source code. The bundled reference advertises skillshub install <owner/repo/skill>[@commit] as supported syntax, but SKILL.md correctly warns that @commit is rejected for non-gist taps, and src/registry/skill.rs:129-131 hard-errors with Pinned commits are not supported for git-based taps. An agent loading both files into context will pick up the syntax from the reference and confidently suggest a command that always fails. Either drop [@commit] from this line, or annotate it as gist-only.

2. docs/plans/2026-05-07-empty-default-tap.md:4 (90) — **Status**: Draft — awaiting review is stale: the plan is fully implemented by commit 7cce504 in this same PR. CLAUDE.md says: "After the plan is fully implemented, rewrite it as a design doc in docs/, and remove it from plans/." At minimum flip the status to Implemented; ideally promote the file to a design doc (e.g. docs/empty-default-tap.md) and drop it from docs/plans/.

Minor (confidence 75-89)

3. PR description test plan (85) — only 2 of 7 items are checked. The 5 unchecked items (install resolves, info shows metadata, link symlinks the skill, bundled references/ ride along after install, README Quick Start examples actually install) cover precisely the behavior this PR changes — and cargo test doesn't exercise any of them because the test fixtures don't read the real skills/ directory. Worth running them locally and ticking the boxes (or noting why they're being deferred) before merge.

Positive observations

• Plan was committed before the implementation (f67bd67 then 7cce504) — good process.
• The code-reviewer → using-skillshub substitution is consistent across src/cli.rs, README, CLAUDE.md, AGENTS.md, and CHANGELOG. No stale references to the 13 removed skills remain in source or docs.
• 17-agent list is identical across src/agent.rs::KNOWN_AGENTS, SKILL.md, the bundled architecture.md, and README — no drift.
• SKILL.md description is a strong trigger string (covers both what and when, with concrete trigger phrases).
• references/cli-reference.md and references/architecture.md are byte-identical copies of the canonical docs at PR-head — the acknowledged drift tradeoff hasn't materialized yet.

[EYH0602]

Addressing the three findings.

1. cli-reference.md:13 [@commit] contradiction (95) — fixed in both bundled and canonical files (see thread reply). Removed the bracket syntax rather than annotating it gist-only, since gists are installed via skillshub add <gist-url> and never via this install <owner/repo/skill> form. The SKILL.md warning at lines 197-199 already covers the nuance for agents.

2. docs/plans/2026-05-07-empty-default-tap.md stale status (90) — fixed by promoting to docs/empty-default-tap.md (concise design doc) and removing the plan, per the explicit CLAUDE.md rule. See thread reply.

3. PR description test plan (85) — already addressed: all 7 boxes are currently ticked in the PR body, including the 5 the review flagged (install resolves, info shows metadata, link symlinks, bundled references/ ride along, README Quick Start examples). The review must have rendered against an earlier revision of the description.

Build still passes after the doc changes (cargo build); no source code touched. Will let the human commit.

[fenfenai]

Re-review: all findings addressed

Verified the two new commits (3110b02 version bump, 7724de0 doc fixes) at head 7724de0.

Resolved

1. @commit contradiction — Fixed in both skills/using-skillshub/references/cli-reference.md:13 and the canonical docs/cli-reference.md:13. Both now show skillshub install <owner/repo/skill> with no bracket. Consistent with src/registry/skill.rs:130 and the SKILL.md warning.
2. Plan status — Cleanly handled per CLAUDE.md: docs/plans/2026-05-07-empty-default-tap.md deleted, replaced by a concise design doc at docs/empty-default-tap.md with **Status**: Implemented. The new doc preserves the load-bearing decisions (bundle-references-inside-the-skill, out-of-scope invariants) without retaining the implementation-step noise.
3. Test plan — All 7 items now checked.

New commits also reviewed

• Cargo.toml 1.0.3 → 1.1.0: minor bump is reasonable — the binary's CLI surface is unchanged; only the default-tap contents changed. Cargo.lock updated to match.
• CHANGELOG: [Unreleased] retitled to [1.1.0] - 2026-05-07 and backfilled with [1.0.1], [1.0.2], [1.0.3] entries. The backfills accurately match the commit history (multi-byte UTF-8 fix → 1.0.1, OpenCode path fix → 1.0.2, Kiro + 6 agents → 1.0.3).
• Design doc: docs/empty-default-tap.md is well-scoped — rationale + key decisions + scope boundaries, no leftover implementation steps.

Resolving both inline threads. Approving.