Show real mapping grammar in --help, make --via repeatable, trim comments

- -l/-r/-d now show their actual grammar as the clap value name
  (<[BIND:]PORT:HOST:PORT>, <[BIND:]PORT>) instead of a generic <SPEC>,
  matching vmic's convention of showing real syntax in --help. The
  grammar is no longer also repeated in the flag's help text, since the
  value name already carries it.
- --via changes from a single comma-separated flag to a repeatable one
  (Vec<String> + value_delimiter = ','), so both `--via a --via b` and
  `--via a,b` work and can be mixed. commands/mod.rs's edits_from_mapping
  no longer needs to split the string itself - clap does it.
- Trimmed CLI help text that restated grammar/rationale already covered
  by the value name or by --via being required.
- Normalized code comments for tone/format consistency: dropped
  cross-references to vmic's own internals as justification (this
  codebase should read as self-contained), removed markdown-style
  *emphasis* asterisks that don't render in plain comments, tightened
  several run-on sentences into plain declarative ones, and fixed one
  comment in wipe.rs that inaccurately described close_instance's force
  path (it sends SIGKILL, not SIGTERM).
- spec/porthole-spec.md's --via row updated to document the repeatable
  form alongside comma-separated.

Cargo.toml/Cargo.lock/atomic.rs also carry an external toml crate bump
and formatting pass picked up from the working tree.

spec/porthole-spec.md

@@ -204,7 +204,7 @@ Saves a new profile. Does **not** open it.
 | `-l, --local`      | `[bind:]port:host:hostport`   | one of `-l/-r/-d` | —                         | Local forward: your machine → remote   |
 | `-r, --remote`     | `[bind:]port:host:hostport`   | one of `-l/-r/-d` | —                         | Remote forward: remote → your machine  |
 | `-d, --dynamic`    | `[bind:]port`                 | one of `-l/-r/-d` | —                         | Dynamic forward (SOCKS proxy)          |
-| `--via`            | `[user@]host[:port][,...]`    | **yes**            | —                         | Comma-separated hop chain; the *last* hop is the actual `ssh` connection target, any before it are `-J` jumps (§3.1) |
+| `--via`            | `[user@]host[:port]`          | **yes**            | —                         | One hop chain entry; repeatable (`--via a --via b`) and/or comma-separated (`--via a,b`) - the last hop is the `ssh` connection target, any before it are `-J` jumps (§3.1) |
 | `-u, --user`       | `user`                        | no                 | current user / ssh_config | Default user for the final target and any `--via` hop that doesn't specify its own |
 | `-i, --identity`   | `path`                        | no                 | ssh_config default        |                                        |
 | `-p, --port`       | `port`                        | no                 | `22`                      | SSH port on the final target only — a `--via` hop needs its own inline `:port` if it isn't 22 |