feat: matrix support (part 1) (#242)

* feat(channel): add Matrix adapter support

* fix(channel): prevent reasoning leaks in Matrix replies

* fix(channel): persist Matrix sync cursors

* fix(channel): improve Matrix markdown rendering

* fix(channel): support Matrix attachments and multimodal history

* fix(channel): expand Matrix reply media context

* fix(handlers): allow media downloads for chat-access bots

* fix(channel): classify Matrix DMs as direct chats

* fix(channel): auto-join Matrix room invites

* fix(channel): resolve Matrix room aliases for outbound send

* fix(web): use Matrix brand icon in channel badges

Replace the generic Matrix hashtag badge with the official brand asset so channel badges feel recognizable and fit the circular mask cleanly.

* fix(channel): add Matrix room whitelist controls

Let Matrix bots decide whether to auto-join invites and restrict inbound activity to allowed rooms or aliases. Expose the new controls in the web settings UI with line-based whitelist input so access rules stay explicit.

* fix(channel): stabilize Matrix multimodal follow-ups and settings

* fix(flow): avoid gosec panic on byte decoding

* fix: fix golangci-lint

* fix(channel): remove Matrix built-in ACL

* fix(channel): preserve Matrix image captions

* fix(channel): validate Matrix homeserver and sync access

Fail Matrix connections early when the homeserver, access token, or /sync capability is misconfigured so bot health checks surface actionable errors.

* fix(channel): preserve optional toggles and relax Matrix startup validation

* fix(channel): tighten Matrix mention fallback parsing

* fix(flow): skip structured assistant tool-call outputs

* fix(flow): resolve merged resolver duplication

Keep the internal agent resolver implementation after merging main so split helper files do not redeclare flow symbols. Restore user message normalization in sanitize and persistence paths to keep flow tests and command packages building.

* fix(flow): remove unused merged resolver helper

Drop the leftover truncate helper and import from the resolver merge fix so golangci-lint passes again without affecting flow behavior.

---------

Co-authored-by: Acbox Liu <acbox0328@gmail.com>

go.mod

@@ -123,6 +123,7 @@ require (
 	github.com/valyala/bytebufferpool v1.0.0 // indirect
 	github.com/valyala/fasttemplate v1.2.2 // indirect
 	github.com/yosida95/uritemplate/v3 v3.0.2 // indirect
+	github.com/yuin/goldmark v1.7.13 // indirect
 	go.opencensus.io v0.24.0 // indirect
 	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
 	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.65.0 // indirect