refactor: remove packages/shared, deduplicate with CLI shared (#2257)

* refactor: remove packages/shared, deduplicate with packages/cli/src/shared

packages/shared duplicated packages/cli/src/shared (parse.ts, result.ts,
type-guards.ts) with the CLI never importing from the shared package.
The only consumer was .claude/skills/setup-spa, which now imports directly
from packages/cli/src/shared via relative paths.

- Delete packages/shared entirely
- Update setup-spa imports to use relative paths to CLI shared
- Remove @openrouter/spawn-shared workspace dependency from setup-spa
- Update CLAUDE.md and type-safety.md references

Agent: complexity-hunter
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* fix: remove packages/shared from lint workflow, fix import sorting

The Biome Lint CI step referenced packages/shared/src/ which no longer
exists after this PR removes the package. Also fix import ordering in
setup-spa files to satisfy Biome's organizeImports rule.

Agent: pr-maintainer
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

* fix: address Devin review — update stale packages/shared references

- Update type-safety.md line 67: packages/shared/src/parse.ts → packages/cli/src/shared/parse.ts
- Update install.ps1 sparse-checkout: remove packages/shared reference

Agent: pr-maintainer
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

---------

Co-authored-by: B <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

packages/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@openrouter/spawn",
-  "version": "0.15.5",
+  "version": "0.15.6",
   "type": "module",
   "bin": {
     "spawn": "cli.js"