Drop chcat/chtail/chgrep symlink entrypoints; ship chlog subcommands only

The RPM's /usr/bin/chcat conflicts with SELinux's
policycoreutils-python-utils on Fedora. Per Ben: remove the symlink
entrypoints entirely and ship only the chlog binary with cat/tail/grep
subcommands.

- Remove chcat/chtail/chgrep symlinks and their completions from
  nfpm.yaml, build-rpm.sh and the Makefile
- Remove the argv[0] dispatch in main.go; subcommands are unchanged
- Update the completion test to cover chlog only
- Update README usage to chlog cat|tail|grep

README.md

@@ -1,20 +1,24 @@
 # clickhouse-tools
 
 CLI tools for the ClickHouse log store (`logs.raw`): one binary, `chlog`, with
-three entrypoints installed as symlinks:
+three subcommands:
 
-| Command  | Also as       | Does |
-|----------|---------------|------|
-| `chcat`  | `chlog cat`   | Print logs oldest-first over a bounded time range |
-| `chtail` | `chlog tail`  | Follow logs live (2s poll, overlap + dedupe so nothing is lost or repeated) |
-| `chgrep` | `chlog grep`  | Search log messages (substring, `-i`, `--regex`) |
+| Command      | Does |
+|--------------|------|
+| `chlog cat`  | Print logs oldest-first over a bounded time range |
+| `chlog tail` | Follow logs live (2s poll, overlap + dedupe so nothing is lost or repeated) |
+| `chlog grep` | Search log messages (substring, `-i`, `--regex`) |
+
+(Earlier releases also shipped `chcat`/`chtail`/`chgrep` symlinks; they were
+dropped because `/usr/bin/chcat` conflicts with SELinux's
+`policycoreutils-python-utils` package.)
 
 ## Why time bounds everywhere
 
 `logs.raw` has no text index and holds ~281M rows/day (3-day TTL). An unbounded
 message scan takes ~1 minute and the server kills queries at 120s. Every query
 these tools issue is therefore time-bounded — the default range is the last
-hour (`--since 1h`) — and `chgrep` refuses a search wider than 6h with no
+hour (`--since 1h`) — and `chlog grep` refuses a search wider than 6h with no
 `--namespace`/`--host`/`--app` filter unless you pass `--force`.
 
 All user input travels as ClickHouse HTTP `{name:Type}` parameters; nothing is
@@ -23,12 +27,12 @@ ever interpolated into SQL text.
 ## Usage
 
 ```sh
-chcat -n logging --since 30m
-chcat --host web01 --since 2h --until 1h --format logfmt
-chtail -n media --app jellyfin
-chgrep -n kube-system -i "connection refused" --since 4h
-chgrep --app vector --regex 'timed? ?out' --since 1d
-chgrep --fields req_id=42 -n api "payment"
+chlog cat -n logging --since 30m
+chlog cat --host web01 --since 2h --until 1h --format logfmt
+chlog tail -n media --app jellyfin
+chlog grep -n kube-system -i "connection refused" --since 4h
+chlog grep --app vector --regex 'timed? ?out' --since 1d
+chlog grep --fields req_id=42 -n api "payment"
 ```
 
 ### Common flags
@@ -41,7 +45,7 @@ chgrep --fields req_id=42 -n api "payment"
 - `--format text|json|logfmt` — text is `ts ns/pod msg` (host for vm rows),
   colored only on a TTY (`NO_COLOR` respected)
 
-### chgrep extras
+### chlog grep extras
 
 - pattern is a substring by default; `-i` case-insensitive; `--regex` RE2 (`match()`)
 - `--fields key=value` (repeatable) filters the structured `fields` map
@@ -58,8 +62,8 @@ chgrep --fields req_id=42 -n api "payment"
 ## Build and release
 
 ```sh
-make build        # dist/chlog + symlinks
+make build        # dist/chlog
 make test         # go test -race ./...
-make rpm          # nfpm RPM with binary, symlinks, bash/zsh/fish completions
+make rpm          # nfpm RPM with binary + bash/zsh/fish completions
 make patch        # tag + push next vX.Y.Z → CI releases RPM to artifactapi rpm-internal
 ```