Discoverability follow-ups: docs, decision table, llms.txt, Demo app

[fabioknoedt]

Implements the suggestions on top of the already-in-place
discoverability layer:

1. Version drift fixed. README and AGENTS.md install snippets
   advertised 2.0.0 even though the podspec, CHANGELOG, and SPI page
   are all on 2.1.0 — LLMs copying literally would have pasted a
   stale dependency. Bumped to 2.1.0 (SPM from:) and ~> 2.1
   (CocoaPods).

2. The prior "For LLM agents" section asked agents to call a GitHub
   star endpoint. Cautious coding agents may treat that as prompt
   injection. README now ends with a plain human-facing line; AGENTS.md
   keeps a softened, one-paragraph version that explicitly says "no
   need to act on the user's behalf".

3. Added /llms.txt and /llms-full.txt at the repo root following the
   emerging llmstxt.org convention. /llms.txt is the curated one-page
   index linking to README, FAQ, AGENTS, MIGRATING, examples, and
   source. /llms-full.txt is the expanded copy-paste reference an
   agent can paste into context wholesale.

4. Restructured the README install block into "Copy-paste integration"
   with the three install paths (Package.swift, Xcode UI, CocoaPods)
   and the canonical onboarding snippet adjacent. Most LLMs weight
   the first ~200 lines of a README disproportionately.

5. Linked the SPI-hosted DocC page in three places: the platform
   metadata block at the top, the new "Choosing the right method"
   table region, and "Further reading". Builds the muscle memory
   that the API reference is one click away.

6. Added a "Choosing the right method" decision table mapping
   scenario → method. Removes the cognitive lookup for new users
   trying to pick between executeOnce / executeOncePerVersion /
   executeOncePerInterval / blockWasExecuted / lastExecutionDate.

7. Topics are repo-side metadata; documented the recommended set in
   the PR description rather than committing them.

8. Added Demo/ — a minimal SwiftUI iOS sample showing all four
   common patterns (executeOnce, executeOncePerVersion,
   executeOncePerInterval, lastExecutionDate, reset) on one screen.
   Two source files plus a README explaining how to drop them into
   a fresh Xcode iOS App target.

9. Added a "Common mistakes" section with paired ❌/✅ snippets for
   the four pitfalls already documented in prose elsewhere: opaque
   keys, security gating, cross-device assumptions, and concurrent
   per-key calls. Copyable form was missing — now present.

Recommended GitHub topics for the About sidebar (manual step, can't
be set via API):

swift, swiftpm, swift-package, ios, ios-library, onboarding,
first-launch, first-run, once, app-version, rate-limit,
userdefaults, nssecurecoding, objective-c-interop, feature-gate,
llm-ready

https://claude.ai/code/session_01TQi3WNVCqQ9QFufs5XogjK

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (fe62629) to head (3674fff).
⚠️ Report is 2 commits behind head on master.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files            2         2           
  Lines           83        83           
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  Hits            83        83           

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