fix: declare the tested minimum Pi version in peer dependencies

[dajiaohuang]

Summary

Fixes #11.

The four Pi packages were declared as "*", so npm accepted Pi 0.79.10 even though SoL-Pi cannot load against it. That release predates the @earendil-works/pi-ai/compat export and the agent_settled and sessionEntryToContextMessages APIs SoL-Pi imports.

The declared floor is now 0.81.1, the lowest release docs/compatibility.md records as exercised, and the lockfile root mirrors it. typebox is unchanged, and no Pi package, dependency, or runtime behavior changes.

Regression coverage

Three assertions in tests/package.test.ts keep the declared contract aligned:

• every Pi peer range is identical and not "*", and its floor equals the floor declared in docs/compatibility.md;
• the lockfile root peers match the manifest;
• the declared floor is above 0.79.10.

Each was checked against a deliberate regression. Reverting the manifest ranges to "*" fails all three; reverting only the lockfile entry fails the lockfile assertion, which is the drift this change also fixes.

Validation

• Pi 0.79.10, isolated install: on the unmodified base, node scripts/check-pi-compat.mjs and import('./src/sol-pi/index.ts') both fail with ERR_PACKAGE_PATH_NOT_EXPORTED for @earendil-works/pi-ai/compat. Pi 0.81.1 passes both. * accepts 0.79.10; >=0.81.1 rejects it and still accepts 0.81.1 and 0.84.2.
• npm run typecheck: passed.
• npx vitest run tests/package.test.ts -t "declared Pi compatibility": passed, 3 tests.
• Full suite: 132 passed, 5 failed. The same 5 fail on an unmodified base checkout — two npm pack cases that need a POSIX npm shim, two symlink cases, and one reducer case — so none are regressions. npm run check therefore does not complete on this Windows host; the pack cases are expected to pass in CI.
• node scripts/check-pi-compat.mjs: passed.
• npm ci --ignore-scripts --dry-run: passed.
• npm audit --audit-level=high: passed; the two moderate Vitest advisories are unchanged.

Tested with Node 24.14.1 and Pi 0.84.2.

[gaoanze888]

Reviewed against the reproduction in #11. The metadata change is focused: the four shared-release Pi peers now use the documented, exercised 0.81.1 floor, with the lockfile and compatibility docs kept in sync. I ran npm run check locally: typecheck, 17 test files / 137 tests, and package dry-run all passed.

The added package-contract tests explain most of the diff and cover the important drift modes (wildcard ranges, package/lockfile mismatch, and the known-incompatible 0.79.10 boundary). I did not find a blocking correctness issue. Thanks for turning the issue into a well-scoped compatibility fix.