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.

crates/irtt-cli/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-cli"
-version = "0.4.0"
+version = "0.5.0"
 description = "Command-line IRTT-compatible client and server"
 edition.workspace = true
 license.workspace = true

crates/irtt-client/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-client"
-version = "0.4.0"
+version = "0.5.0"
 description = "IRTT-compatible Rust client library"
 edition.workspace = true
 license.workspace = true

crates/irtt-proto/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-proto"
-version = "0.4.0"
+version = "0.5.0"
 description = "IRTT protocol encoding and decoding primitives"
 edition.workspace = true
 license.workspace = true

crates/irtt-server/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-server"
-version = "0.4.0"
+version = "0.5.0"
 description = "IRTT-compatible Rust server library"
 edition.workspace = true
 license.workspace = true

crates/irtt-stats/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "irtt-stats"
-version = "0.4.0"
+version = "0.5.0"
 description = "Statistics aggregation for irtt-client events"
 edition.workspace = true
 license.workspace = true