Fix cligen schema walker to recurse through nested array items

[ysyneu]

What

The request/response field-tree walker in internal/cmd/cligen/main.go only unwrapped one array level before checking whether the element schema was an object. A nested array field — the OR-of-AND filter tree shape used by filters/source_filters/target_filters across silence, escalate, inhibit, and unsubscribe rules (array<array<object>>) — never expanded its key/oper/vals item fields the way a plain array<object> field (e.g. layers) already did. The type label had the same bug, collapsing to the uninformative array<array> instead of array<array<object>>.

Both --help and the skill-card generator (internal/skilldoc) read from this same walker's output, so the gap showed up in both places.

Fix

• tree()'s array case now unwraps items through any depth of nested arrays (via a new arrayLeafSchema helper, bounded defensively) before testing for an object leaf — generalized, not special-cased per command.
• schemaType() is now recursive for the same reason, so nested array type labels show their real depth (array<array<object>>, array<array<string>>, …).
• Regenerated all zz_generated_*.go command files and the skill-card fences (go run ./internal/cmd/cligen + go run ./internal/cmd/skilldoc gen). Affected commands: escalate-rule-create/update (filters), inhibit-rule-create/update (source_filters/target_filters), silence-rule-create/update (filters), unsubscribe-rule-create/update (filters), plus the alert-pipeline read paths that document the same filter shape (if, nested source_filters).
• Added unit tests: nested array-of-object expansion, nested array-of-scalar (no false-positive children), the type-label recursion, and a regression guard on the existing single-level array<object> behavior.

Card content

skills/flashduty/reference/channel.md's hand-written "add a silence rule during maintenance" flow previously built a rule from only a time_filter, which the server rejects (no matching scope). Replaced it with a flow that pulls the target incident's labels and builds filters from them, and added a general "Building filters from incident labels" rule: base severity condition, per-label conditions with exclusions for id-shaped/long/date-shaped/noise-key values, the valid key vocabulary and oper enum, a note that an out-of-vocabulary key silently never matches instead of erroring, and verifying via the matching *-rule-list command.

Verification

• make check (fmt, lint, go test -race ./..., build): all green, 0 lint issues, no test failures.
• go run ./internal/cmd/skilldoc check: cards OK.
• ./bin/flashduty channel silence-rule-create --help confirms filters now renders key/oper/vals children with descriptions and the IN/NOTIN enum.

Follow-up (not in this PR)

fc-safari holds its own copy of this fence at logic/runtime/bootstrap/skills/flashduty/reference/channel.md and needs a resync after this merges. No other repo under the org was found holding a copy.