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>

vendor/modernc.org/sqlite/CONTRIBUTORS

@@ -0,0 +1,48 @@
+# This file lists people who contributed code to this repository.  The AUTHORS
+# file lists the copyright holders; this file lists people.
+#
+# Names should be added to this file like so:
+#     Name <email address>
+#
+# Please keep the list sorted.
+
+Adrian Witas <adrianwit@gmail.com>
+Alexander Menzhinsky <amenzhinsky@gmail.com>
+Alexey Palazhchenko <alexey.palazhchenko@gmail.com>
+Angus Dippenaar <angusdippenaar@gmail.com>
+Artyom Pervukhin <github@artyom.dev>
+Dan Kortschak <dan@kortschak.io>
+Dan Peterson <danp@danp.net>
+David Skinner <skinner.david@gmail.com>
+David Walton <david@davidwalton.com>
+Elle Mouton <elle.mouton@gmail.com>
+FlyingOnion <731677080@qq.com>
+Gleb Sakhnov <gleb.sakhnov@gmail.com>
+Guénaël Muller <inkey@inkey-art.net>
+HaoZi <haozi@loli.email>
+Harald Albrecht <thediveo@gmx.eu>
+Ian Chechin <ian00chechin@gmail.com>
+Jaap Aarts <jaap.aarts1@gmail.com>
+Jan Mercl <0xjnml@gmail.com>
+Josh Bleecher Snyder <josharian@gmail.com>
+Josh Klein <josh.klein@outlook.com>
+Kim <grufwub@gmail.com>
+Logan Snow <logansnow@protonmail.com>
+Mario Salgado <mariozalgo@gmail.com>
+Mark Summerfield <mark@qtrac.eu>
+Matthew Gabeler-Lee <fastcat@gmail.com>
+Michael Hoffmann <mhoffm@posteo.de>
+Michael Rykov <mrykov@gmail.com>
+Morgan Bazalgette <morgan@howl.moe>
+Prathyush PV <prathyush.pv@temporal.io>
+Romain Le Disez <r.gitlab@ledisez.net>
+Ross Light <ross@zombiezen.com>
+SUSE LLC <legal@suse.de>
+Saed SayedAhmed <saadmtsa@gmail.com>
+Sean McGivern <sean@mcgivern.me.uk>
+Steffen Butzer <steffen(dot)butzer@outlook.com>
+Toni Spets <toni.spets@beeper.com>
+W. Michael Petullo <mike@flyn.org>
+Walter Wanderley <walterwanderley@gmail.com>
+Yaacov Akiba Slama <ya@slamail.org>
+Zhenghao Zhang zhangzhenghao@hotmail.com