docs: point the READMEs at the published 0.28.0 packages

[kivtxs]

0.28.0 put the Python binding on PyPI and shipped a Swift package and an Android download, but the two READMEs still told everyone to build from source and pip install -e .. This points them at the published packages and keeps the source build for contributors and for hosts without a package. Docs only; CHANGELOG and UPGRADING are untouched.

PyPI timing. bindings/python/README.md is the PyPI long description, and PyPI shows the README of the published version. The 0.28.0 page keeps the old text (build from source, and the user_id= example below), so this fix appears on PyPI with the next release.

README.md

• An Install section: npm, PyPI with the exact wheel platforms, crates.io (cargo add offline-protocol), the Swift package as a preview, and the Android release download as a preview.
• Swift: the product, iOS 13 or later, iOS only, and the package's own status in plain words: the storage providers are not public, the app wires the transports, and the API may change.
• Android: the coordinates com.offlineprotocol:offline-protocol-sdk are named, with the fact that they are not on Maven Central yet (MAVEN_CENTRAL_PUBLISH is off, and repo1 returns 404). The release zip holds the generated Kotlin bindings and jniLibs for four ABIs, without the transport managers, and the full AAR is built from bindings/kotlin. There is no Gradle line that would fail to resolve.
• The Python quick start installs from PyPI. pip install -e . moves to "Build Python Desktop Bindings".
• PyPI and crates.io badges. The Features line mentions the early native packages.
• The React Native example sends to peerAddress instead of 'recipient456'. Since 0.21.0 a username reaches nobody (UPGRADING §14).

bindings/python/README.md (the PyPI page)

• The quick start starts with pip install offline-protocol-sdk and a wheel table: Python 3.10 or later, macosx_14_0_arm64, manylinux_2_34_x86_64 and manylinux_2_34_aarch64 (glibc 2.34 or later), and win_amd64. It also says there is no Intel macOS wheel, no musl wheel and no sdist, so those hosts build from source.
• "Building from source" now comes after the usage example and starts with git clone.
• The usage example was broken: it passed ProtocolConfig(user_id=...), which has been profile= since 0.21.0. With the published 0.28.0 wheel it raises TypeError: ProtocolConfig.__init__() got an unexpected keyword argument 'user_id'. It now passes profile= and sends to a peer address.
• pm.internet.configure(server_url=...) is correct as written: ProtocolManager builds the InternetManager with app_id=config.app_id. The upgrade note now says that an InternetManager you construct yourself needs app_id= (UPGRADING §26).
• The Platform Support table gains a "Wheel on PyPI" column.
• Second commit: ten links were repository-relative (spec chapters, local API, file stores, telemetry), and on PyPI each one 404s. The file's own License section says its links are absolute for that reason, so these now point at blob/main like the rest. Every target exists. It is a separate commit, so it can be dropped on its own.

Checks

• The corrected example ran against the published wheel (pip install offline-protocol-sdk==0.28.0, Python 3.12, macOS arm64). It used in-memory storage providers and a local WebSocket server in place of the keyring and relay. Config, async with ProtocolManager(...), pm.internet.configure/start and send_message all succeeded.
• scripts/check-license-consistency.sh and scripts/check-crate-readmes.sh pass.
• I resolved every ](path#anchor) in every tracked markdown file against the files and headings that exist, as CONTRIBUTING asks. The touched files have no broken links, and the tree has the same result before and after this change (the only two hits are the example ](docs/…) strings inside CONTRIBUTING's prose).
• readme_renderer (the renderer PyPI uses) renders the Python README cleanly, and #building-from-source resolves.
• No em dashes in added text.

Left alone

• CHANGELOG.md and docs/UPGRADING.md.
• The Architecture list in README.md does not name offline-protocol-telemetry-wire, the twelfth published crate.
• The Python README's "Running the Example" section uses repository paths (examples/basic_messaging.py), and the example's own docstring still says to build from source.