fix(drivers): complete the Sql + FOCAS in-place config re-parse (#516)

The first #516 pass deliberately left these two out, because each derives more
than options from config: Sql its ISqlDialect and resolved connection string,
FOCAS the IFocasClientFactory its Backend key selects — all injected at
construction. Adopting new options alone would poll a NEW tag set through the
OLD database/backend, and a half-applied config change is worse than a
discarded one because it looks like it worked.

Rather than accept that exclusion, this fixes the blocker. Each factory now
exposes a ParseBinding returning EVERY config-derived dependency as one value,
and the driver adopts them atomically:

- Sql: ApplyBinding takes (options, dialect, connectionString) and rebuilds
  everything downstream — provider factory, Endpoint, and the SqlPollReader
  that captures all three. It runs BEFORE BuildTagTable, so the tag table and
  the connection it is polled over always come from the same revision. A
  test-injected DbProviderFactory survives a rebind (_explicitFactory), so a
  re-derived dialect cannot displace what a test passed in.
- FOCAS: options and backend move as a pair in InitializeAsync.

Re-resolving Sql's connection string on reinit is a side benefit: a rotated
credential is picked up without a process restart.

Drivers constructed directly get no rebinder and keep their constructor
binding, so every existing "{}"-passing lifecycle test is unaffected by
construction rather than by luck.

The tests pin ATOMICITY, not merely that a re-parse happened — a test checking
only options would have passed against the broken version. Confirmed by
simulating the half-fix (adopt options, skip the backend): 2 of 3 FOCAS tests
go red. Reverting Sql's rebind turns its connection-string test red. Sql also
asserts that a reinit which cannot resolve its new connection leaves the
previous binding whole rather than half-adopting.

All 12 drivers now honour a changed config in place. Sql.Tests 226, FOCAS.Tests
275 pass.

deferment.md

@@ -497,6 +497,39 @@ describes for Tier C no longer exists (Galaxy went to the mxaccessgw sidecar in
 in-process when its managed wire client landed). No runtime change — turning recycle on for two live
 drivers deserves its own live gate, not a docs-pass side effect. Tracked as Gitea **#522**.
 
+### 2026-07-28 — the two things §8.3 deliberately did NOT build (1 of 2)
+
+**Sql and FOCAS now re-parse in place too.** The first pass excluded them for a real reason — each derives
+more than options from config, so adopting new options alone would run a **new tag set against an old
+connection/backend**, and a half-applied change is worse than a discarded one because it looks like it
+worked. Rather than accept that, the blocker itself is fixed: each factory now exposes a **`ParseBinding`**
+that returns *every* config-derived dependency as one value, and the driver adopts them **atomically**.
+
+| Driver | What one parse now yields | Adopted by |
+|---|---|---|
+| Sql | options + `ISqlDialect` + resolved connection string | `ApplyBinding`, which also rebuilds the provider factory, `Endpoint` and the `SqlPollReader` that captures all three |
+| FOCAS | options + the `IFocasClientFactory` the `Backend` key selects | one assignment pair in `InitializeAsync` |
+
+Details worth keeping:
+
+- **Sql adopts BEFORE `BuildTagTable`**, so the tag table and the connection it will be polled over always
+  come from the same revision.
+- **A test-injected `DbProviderFactory` survives a rebind** (`_explicitFactory`), so a re-derived dialect
+  cannot silently displace what a test passed in.
+- **Re-resolving the connection string on reinit is a side benefit**: a rotated credential is picked up
+  without a process restart.
+- A driver constructed **directly** gets no rebinder and keeps its constructor-supplied binding — every
+  existing `"{}"`-passing lifecycle test is unaffected by construction, not by luck.
+
+**The tests pin ATOMICITY, not merely "a re-parse happened"** — a test that only checked options would have
+passed against the broken version. Verified by simulating the *half-fix* (adopt options, skip the backend):
+2 of the 3 FOCAS tests go red. Reverting Sql's rebind turns its connection-string test red. Sql also asserts
+that a reinit which **cannot resolve** its new connection leaves the previous binding whole, rather than
+half-adopting.
+
+All 12 drivers now honour a changed config in place; `DriverSpawnPlanner`'s stop + respawn remains the outer
+guarantee. Sql.Tests 226 / FOCAS.Tests 275 pass.
+
 ### 2026-07-27 — §8.4 dispatch-map parity (G-1 … G-6)
 
 **The maps had to become data before they could be guarded.** A Razor `@switch` compiles into