chore: bump Motoko to v1.6.0

.sources/VERSIONS

@@ -50,7 +50,7 @@ chain-fusion-signer   v0.3.0
 papi                  v0.1.1                                                    168bc9d
 ic-pub-key            v1.0.1                                                    f89fa55
 icp-cli               v0.2.3                                                    caeac37
-motoko                v1.5.1  # tag 8e4c02d not in shallow clone                395ce0b
+motoko                v1.6.0                                                     b818df6
 motoko-core           v2.4.0                                                    cd37dbf
 cdk-rs                ic-cdk v0.19.0 / ic-cdk-timers v1.0.0 / ic-cdk-executor v2.0.0  80d8234
 candid                2025-12-18  # candid v0.10.20, didc v0.5.4                2e4a2cf

docs/languages/motoko/reference/changelog.md

@@ -22,6 +22,14 @@ $(dfx cache show)/moc --version
 
 # Motoko compiler changelog
 
+## 1.6.0 (2026-04-21)
+
+* motoko (`moc`)
+
+  * bugfix: Fix `moc.js` resolution of relative flag paths (e.g. `--enhanced-migration`, `--actor-idl`): resolve against the project root (via new `setProjectRoot` API) instead of the source file's directory, matching native `moc` behavior. The language server should call `setProjectRoot(path)` before processing files.
+
+  * feat: expose caller attributes feature through prim (#5970)
+
 ## 1.5.1 (2026-04-13)
 
 * motoko (`moc`)