chore(release): move to independent per-crate versioning at 0.5.0

Each workspace crate now owns its own version instead of the previous
lockstep scheme; irtt-proto, irtt-client, irtt-server, irtt-stats, and
irtt-cli all become 0.5.0 as the first independently-versioned release.
Workspace dependency requirements are bumped to match.

Add a root CHANGELOG.md with a real per-crate 0.5.0 section drawn from
archaeology of every merge since v0.4.0, not just path-filtered commits.

Move cargo-dist to a crate-qualified `irtt-cli/vX.Y.Z` tag namespace so
only irtt-cli (the one dist-able application) triggers a GitHub Release;
library crate tags (irtt-proto/irtt-client/irtt-server/irtt-stats) exist
purely to pin the source for a crates.io release and no longer risk
tripping the release workflow. Regenerate the renamed
irtt-cli-release.yml via `dist generate` and update the few other files
that referenced the old release.yml path by name. Also fix a stale
`features = ["full"]` in dist-workspace.toml left over from a feature-flag
refactor that dropped the "full" feature entirely, which was silently
breaking every dist build.

Rescope semver.yml's tag trigger to the same five crate-qualified tags
so semver checks keep running under the new convention.

Cargo.lock

@@ -694,7 +694,7 @@ dependencies = [
 
 [[package]]
 name = "irtt-cli"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "clap",
  "crossterm",
@@ -709,7 +709,7 @@ dependencies = [
 
 [[package]]
 name = "irtt-client"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "irtt-proto",
  "irtt-server",
@@ -721,7 +721,7 @@ dependencies = [
 
 [[package]]
 name = "irtt-proto"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "hmac",
  "md-5",
@@ -731,7 +731,7 @@ dependencies = [
 
 [[package]]
 name = "irtt-server"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "getrandom 0.4.3",
  "irtt-client",
@@ -744,7 +744,7 @@ dependencies = [
 
 [[package]]
 name = "irtt-stats"
-version = "0.4.0"
+version = "0.5.0"
 dependencies = [
  "irtt-client",
 ]