Managed modelPricing in the cost estimator: three layers, one number

Issue #3878, second half. #3885 pinned the vocab to the binary's price tiers. This change makes the estimator honour the org override CC itself honours, so an org on a contract sees the same figure in /ork:analytics as in /cost.

What CC 2.1.258 does with modelPricing (read from the binary)

field	rule
`multiplier`	number in (0, 1]; "scales every computed cost, overridden or not (0.85 = 85% of the price)"
`overrides[modelId]`	`{ input, output, cacheRead, cacheWrite }`, all four required, each 0 to 10000, USD per million tokens; `cacheWrite` prices both the 5-minute and the 1-hour write
key matching	case-insensitive; a built-in ID covers its dated and provider forms; the earlier row wins a duplicate
bad input	"An invalid row or multiplier is reported and skipped; the rest still apply"
sources	managed only: server-managed, MDM/OS policy, or `managed-settings.json`; ignored in user, project, local and `--settings`

Paths: /Library/Application Support/ClaudeCode/managed-settings.json (macOS), /etc/claude-code/managed-settings.json (Linux, WSL), C:\Program Files\ClaudeCode\managed-settings.json (Windows).

Precedence, lowest to highest

models.vocab.json  <  ~/.claude/orchestkit-pricing.json  <  managed modelPricing.overrides
                                                            then  x  modelPricing.multiplier on every rate

Layers 1 and 2 already existed. Layer 3 and the multiplier are new. Try them: the table below is the estimator's getCostConfig().models for the current Fable, computed the same way the TypeScript does it.

multiplier (blank = none)

override input $/MTok

override output $/MTok

override cacheRead $/MTok

override cacheWrite $/MTok

layer 2: orchestkit-pricing.json sets input to $1 (a stale local override)

layer 3: managed override row for claude-fable-5-1

claude-fable-5-1	input	output	cache read	cache write	1M in + 1M out
vocab (list, layer 1)	10	50	0.25	12.5	$60.00
effective

What the tests pin

case	expected
no managed file, or a file without `modelPricing`	list price, no stderr
multiplier only (0.85)	every rate of every vocab model x0.85
override for a known model	that row replaced; alias and `[1m]` variant follow; other rows at list
override for an unknown model	priced by the row instead of the sonnet fallback
multiplier 1.5, 0, -0.2, "abc", null	ignored, one stderr line, overrides in the same file still apply
malformed JSON, non-object block, incomplete or >10000 row	skipped, one stderr line per process, never a throw
managed override vs orchestkit-pricing.json vs vocab	managed wins, user file second, multiplier last on all three
the 12 existing #2338 canaries, incl. the per-model cache-rate exception	unchanged, now hermetic (the machine's real managed file can no longer leak in)

Still open on #3878 after this change

managed-settings.d/ drop-ins, MDM and server-managed policy sources, and the host-application fallback are not read; those users still see list price here. The optional local pricing canary (claude -p --output-format json reproduced to the cent, real API call, never in CI) is not built.