fix(examples): rename example dirs keeper -> strongroom, matching the README

[askalf]

The rename (#30) updated the README's example links to examples/*-strongroom but the directories stayed at *-keeper, so all three README example links 404. This renames the dirs (git mv, history preserved), the example package.json names, and the cd lines + cross-links inside each example README. evidence/ capture files are untouched - they're historical receipts of past runs. No CI or npm-package surface references these paths (files: excludes examples).

[sprayberry-reviewer]

Automated review from the Sprayberry Labs fleet code reviewer (sprayberry-reviewer bot — independent, gating review).

Verdict: no blocking issues found — approved.

What I checked

This is a pure rename PR: three example directories (*-keeper → *-strongroom) moved with git mv, history preserved, and 9 lines of path/name references updated to match. I reviewed:

1. All 9 changed lines across the three README.md files and three package.json files — each cd examples/*-keeper becomes cd examples/*-strongroom, cross-links to sibling dirs are corrected, and package.json "name" fields are updated to *-strongroom-example. All six changes are consistent and correct.

2. No stale examples/*-keeper path references remain anywhere in the example READMEs, .mjs source files, or root README.md. The root README was already updated (in PR #30) to reference the strongroom paths; this PR makes the directories themselves match.

3. keeper occurrences in .mjs and README prose are all product-name references (the CLI tool, vault, broker, keeper-home working directory, KEEPER_* env vars) — none are directory-path references, and none are stale.

4. evidence/ files are intentionally untouched (all similarity index 100%, content unchanged) — they are historical run receipts, not updated by renames, as the PR description explains.

5. No CI or npm-package surface references the old examples/*-keeper paths (confirmed by the PR description noting files: excludes examples/).

What's good

The fix is exactly scoped: rename the directories to match what the README already advertised, update the minimal set of path strings that changed meaning, and leave everything else alone. No collateral changes, no drift.