Prepare v0.2.9 release documentation through SQL name-resolution hardening

[Gokhan Gulbiz (gokhangulbiz)]

Summary

Release preparation for #416, rebased onto current main at 584298de52c8df1064fab4eb5880b233612ee3db (#418), including #401 and every merged change since v0.2.8.

This PR is now documentation-only:

• Curate the full v0.2.9 user-facing history and refresh the planned release date to October 7.
• Include Schema-qualify functions/types/etc in our SQL wherever possible #418's SQL name-resolution hardening and document its binary, schema and replay compatibility considerations.
• Preserve control-first upgrade guidance, HTTP startup-policy migration and endpoint regrant warnings, and accurate origin/explicit-target sink behavior.

No production code, tests, manifests, dependencies, extension DDL or shipped migrations differ from the new main baseline.

Rebase and prior test-isolation work

#418 already includes this PR's original committed-metadata test-isolation fix. The rebase dropped 06f51899 as already upstream rather than duplicating or reverting it. The private-database fixtures, shared df.start() probes and panic-cleanup regression remain in the inherited main code.

The original PG17 merge failure and successful prior preparation CI are historical evidence, not checks for the rebased PR head.

Validation and release gates

• New baseline main CI passed PG17 and PG18 plus macOS source installation; Docker CI also passed at 584298de.
• Confirmed this rebased branch's source, tests, SQL, Cargo manifests/lockfile and packaging metadata are identical to the new main baseline; git diff --check is clean.
• Fresh PR CI is required for rebased head 49079928ec372fa659a6ddb7c93c2fa19637923d; the eventual merged main SHA must be checked separately before tagging.
• Version remains 0.2.9. All previously shipped migrations remain unchanged; Schema-qualify functions/types/etc in our SQL wherever possible #418 needs no added upgrade DDL or schema detection and preserves user SQL search paths and orchestration-generated row-set SQL spelling.

Upgrade and known limitations

Install/restart the new binary and wait for a ready control runtime before creating satellites. Existing control schemas from 0.2.2 onward remain supported; schema update adds the new APIs, and existing HTTP users need grants reapplied for typed endpoints. Previously HTTP-disabled builds must explicitly configure pg_durable.http_security = 'disabled' before restart.

Runtime descendant shutdown and confirmed PostgreSQL backend cancellation/quiescence remain deferred. DROP is not a cancellation acknowledgment or activity-long drain. Already-admitted remote SQL/HTTP can finish after source removal; admission check and send are not atomic with DROP.

Publication remains gated

The rebase and exact-SHA lease-protected branch update were explicitly approved. Merge, tagging an exact green main SHA, and public publication still require separate approval.

Package Release does not run for documentation-only PR paths, and manual dispatch requires an existing v-tag. The supported exact-candidate PG17/PG18 package validation runs on the approved tag, before automated draft creation and public publication; unrelated-SHA package results are not substituted. Public release publication subsequently triggers GHCR and stable PGXN upload.

[Thom Chiovoloni (thomcc-work)]

Looks good. I'll write better relnotes for the tag on the Releases page, but this can land.