fix(skills): cite the cost model instead of repeating prices

The multipliers live in cost-control. Repeating the numbers in three more skills
means they go stale in three more places the next time pricing moves, and a
skill that quotes a wrong price is worse than one that quotes none.

The wording keeps what made the change work: the cost warning stays at the point
of temptation, next to the flag, and it still says which direction is expensive.
Only the figure moves to the one file that owns it.

Author: StefanoGuerrini

skills/extract/SKILL.md

@@ -31,6 +31,7 @@ zenrows extract <url> --validate                   # fail if not valid JSON
 - If Autoparse misses fields, switch to `--css` with explicit selectors. Auto
   mode already renders JS when the target needs it, so reach for
   `--manual --js-render` only after auto mode has returned an incomplete page:
-  it costs 5 credits per request against 1, and it makes the escalation yours.
+  it costs several times a basic call ([[cost-control]]) and it makes the
+  escalation yours.
 
 See [[protected-fetch]] for retrieval semantics.

skills/protected-fetch/SKILL.md

@@ -31,13 +31,14 @@ Manual mode exists for the rare case where auto mode has already failed and a
 trace shows why. It costs more and it makes the escalation your problem:
 
 ```
-zenrows fetch <url> --manual --js-render --premium-proxy   # 25 credits per request
+zenrows fetch <url> --manual --js-render --premium-proxy   # the most expensive path, see [[cost-control]]
 ```
 
 ## Rules
 - Start with **auto mode**. Enabling `--js-render` and `--premium-proxy` yourself
-  costs 25 credits per request against 1 for a basic call, and auto mode reaches
-  the same configuration only when the target actually needs it.
+  is the most expensive configuration this API offers, by a wide margin, and auto
+  mode reaches the same place only when the target actually needs it. The
+  multipliers are in [[cost-control]].
 - A hard target is not a reason to skip auto mode. It is the reason auto mode
   exists.
 - In auto mode `js_render` and `premium_proxy` are managed for you. Passing them

skills/trace-debug/SKILL.md

@@ -22,8 +22,9 @@ zenrows trace export <run-id>     # JSON for sharing
 - `FETCH_FAILED` / empty content → first retry in auto mode (`mode=auto`), which
   escalates for you and bills only for what succeeds. For slow pages add
   `--wait-for <selector>`. Only when auto mode has failed on its own, take
-  manual control with `--manual --js-render` (5 credits per request), then
-  `--premium-proxy` (25 with both, against 1 for a basic call).
+  manual control with `--manual --js-render`, then `--premium-proxy`. Each step
+  multiplies the cost of the request, and both together are the most expensive
+  configuration available ([[cost-control]]).
 - `REQUEST_TIMEOUT` → the CLI stopped waiting; the API was reached. Raise
   `--timeout` (default 120000ms, above the API's own 90s budget), or drop
   `--wait-for` so the request finishes inside that budget and the API returns