fix(ci): repair docs deployment and validate the reviewed release transition

[samheutmaker]

The docs deployment fails on a clean checkout because SDK example tests need generated protocol declarations. Set up the pinned Go toolchain and generate/build the protocol and SDK before those tests, matching regular docs CI.

The development-to-main release also compares protocol 6.9 with an older 6.8 main. Record the exact pre-reorganization changes already present in the frozen development baseline: concrete effort defaults, title ownership/events and input provenance, folder creation, conversation-based compaction defaults, and assistant recording timestamps. Source commits and observable differences are documented in docs/release-readiness.md.

The release expectation applies only to main 88764670f1c6e2a57e22463e96cfb0d6021aea33 and frozen baseline 271c0f8d2a35648d1b45056d57432590b783483c. It checks the original values and requires the expected transcript to match the independently built frozen reference and candidate. Every other PR base retains strict equality. Fixed-SDK, generated artifacts, lifecycle and persisted-data/trace rollback checks remain enabled. There are no runtime, SDK, protocol, schema or baseline-pin changes.

Validation:

• Reproduced the docs example failure before generation; all six example tests pass afterward.
• All 26 comparator and release-transition tests pass, including rejection of extra response, event order/count, cursor, identity, effort and provider changes.
• Exact release expectations match the historical Linux and macOS CI transcripts.
• Full local main-to-candidate compatibility passes for Unix and WebSocket, mutation detection, lifecycle, schema integrity, retained root/child state, tracing and base → candidate → base rollback.
• All 77 docs tests and 27 browser tests pass; target-specific packaging and the preview Worker smoke pass with JavaScript on/off.
• Staged native desktop lifecycle smoke passes (daemon reuse, restored hosts/tabs, settings and tab interactions).
• Additional renderer acceptance found a pre-existing REPL Latest navigation bug; a separate UI repair will land before release: backend reorganization and verified development changes #286 is merged. It does not require SDK/protocol changes.

Prepares #286 for the approved release to main.