fix(map): cargo tree's output is read uncolored

[cryptskii]

What

The Code map job fails on main since #1051. CI sets CARGO_TERM_COLOR=always, so cargo tree wraps its (*) repeat marker in ANSI escape codes, and the map's feature reader refuses those lines:

requirement_map: "proc-macro2 v1.0.106 default,proc-macro \u{1b}[33m\u{1b}[2m(*)\u{1b}[39m\u{1b}[22m" is not a `cargo tree -f '{p} {f}'` line

The fix has two parts:

• Every cargo tree call in make requirement-map now passes --color never, so its input is plain whatever the environment sets.
• A feature-tree line that still holds escape codes is refused by name, with a message giving the cause and the flag, instead of the generic malformed-line error.

Verification

• Reproduced locally with CARGO_TERM_COLOR=always: 314 lines came out coloured.
• With --color never under the same setting, the output is byte-identical to a plain run.
• CARGO_TERM_COLOR=always make requirement-map builds, with 0 escape codes in the feature files. The readings are unchanged:
  • 63 roots and 7 dead-root candidates;
  • 39 definitions excluded;
  • 8,627 reached, 40 indeterminate and 1,544 dead.
• cargo test -p requirement_map --release: the cfgs tests pass, 9 of 9, including one for coloured input.
• Clippy with -D warnings, make lint and the real-code guard all pass.
• The Gemini push gate is satisfied.