feat(ecosystem): compliant Praxis/Hexis integration + vendored build

Bring the Nexus/Praxis/Hexis integration in line with
MAVEN_ECOSYSTEM_ARCHITECTURE.md:

- Praxis over HTTP: drop the in-process praxis.db open (praxisstore/
  praxistools) and call praxisd's /api/v1/tools/* API via a new praxisClient.
  Honors the "no component reads another's DB" invariant (AC#12).
  PraxisConfig.DBPath -> URL.
- Hexis confirmation gate: mutating capabilities (ReadOnly=false) now park a
  bound pendingHexis confirmation and require a spoken "да" before executing;
  read-only run immediately (AC#7, no auto attention->action).
- Capability safety: >1 verb match is ambiguous -> ask instead of firing the
  first; ambiguous Nexus resolution asks for clarification (AC#2).
- Correlation IDs on Hexis execute, recorded in the cross-service trace.
- Bug: importance arrives as JSON float64 over HTTP, not int.
- Tests: confirm-gate, decline, read-only, and ambiguity paths.

Build: vendor/ bakes in the hexis client (replace-directed at a sibling repo
outside the Docker context); Dockerfile builds from vendor and no longer
`go mod download`s the unreachable replace paths.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

go.mod

@@ -1,23 +1,32 @@
 module github.com/kami/maven
 
-go 1.23
+go 1.25.5
 
 require (
 	github.com/coder/websocket v1.8.12
 	github.com/robfig/cron/v3 v3.0.1
 	github.com/yalue/onnxruntime_go v1.31.0
-	golang.org/x/sys v0.22.0
-	modernc.org/sqlite v1.34.5
+	golang.org/x/sys v0.46.0
+	modernc.org/sqlite v1.54.0
 )
 
+require github.com/kami/hexis v0.0.0
+
 require (
 	github.com/dustin/go-humanize v1.0.1 // indirect
 	github.com/google/uuid v1.6.0 // indirect
+	github.com/kami/praxis v0.0.0
 	github.com/mattn/go-isatty v0.0.20 // indirect
-	github.com/ncruces/go-strftime v0.1.9 // indirect
+	github.com/ncruces/go-strftime v1.0.0 // indirect
 	github.com/remyoudompheng/bigfft v0.0.0-20230129092748-24d4a6f8daec // indirect
-	golang.org/x/text v0.3.0 // indirect
-	modernc.org/libc v1.55.3 // indirect
-	modernc.org/mathutil v1.6.0 // indirect
-	modernc.org/memory v1.8.0 // indirect
+	golang.org/x/text v0.14.0
+	modernc.org/libc v1.74.1 // indirect
+	modernc.org/mathutil v1.7.1 // indirect
+	modernc.org/memory v1.11.0 // indirect
 )
+
+replace github.com/kami/praxis v0.0.0 => /home/kami/apps/praxis
+
+replace github.com/kami/nexus v0.0.0 => /home/kami/apps/nexus
+
+replace github.com/kami/hexis v0.0.0 => /home/kami/apps/hexis