create_linkedin_engagement_retargeting_audience

Create a **LinkedIn Engagement Retargeting** audience: people who already engaged
                with the advertiser's LinkedIn ads, company page, or website. STEP 3 of the flow.

                This is NOT create_retargeting_audience, which imports an audience the ad account
                already has. This builds a NEW LinkedIn DMP segment from the engagement rule defined
                here. Once built it is a normal Metadata audience and can be attached to campaigns.

                **REQUIRED WORKFLOW — do not call this tool first:**
                1. get_linkedin_engagement_source_types → choose `source_platform` + `engagement_trigger`
                2. For every source type EXCEPT WEBSITE: search_linkedin_engagement_sources with that
                   trigger and lookback → collect each chosen result's `id` into
                   `engagement_source_urns`
                3. Call this tool
                Source types, triggers and URNs are LinkedIn's own values, and only steps 1 and 2
                can supply them. Do not invent, guess or reuse one from another account: a value
                that did not come from those steps either fails outright or, worse, is accepted and
                builds an audience that never populates.

                **TWO SHAPES, MUTUALLY EXCLUSIVE — mixing them is rejected:**

                A) NON-WEBSITE (VIDEO_ADS, SINGLE_IMAGE_ADS, DOCUMENT_ADS, CONVERSATION_ADS,
                   LEAD_GEN_FORMS, ORGANIZATION_PAGES):
                   pass `engagement_source_urns`. Do NOT pass page_set_name or url_match_groups.

                B) WEBSITE:
                   pass `page_set_name` and `url_match_groups`. Do NOT pass engagement_source_urns.
                   Metadata creates the LinkedIn page set from those URL rules for you.

                URL MATCH RULES (WEBSITE only) are a LIST OF GROUPS. Rules inside a group are ANDed;
                the groups are ORed. Each rule is {matchType, matchValue}, matchType being EXACT
                ("URL equals"), STARTS_WITH, or CONTAINS.
                  [[A, B], [C]]  means  (A AND B) OR C
                Worked example — "anyone who hit pricing or any demo page":
                  [[{"matchType": "STARTS_WITH", "matchValue": "https://example.com/pricing"}],
                   [{"matchType": "CONTAINS",    "matchValue": "/demo"}]]
                Use one rule per group for a simple OR list, which is what most requests mean. Reach
                for a multi-rule group only for a genuine AND, e.g. a path that also carries a
                campaign parameter.

                WHEN TO USE:
                - "Retarget everyone who watched our video ads in the last 90 days"
                - "Build an audience from people who submitted the lead form"
                - "Create an audience of visitors to our pricing and demo pages"
                - "Retarget people who visited our LinkedIn company page"
                - "Make a warm audience from last quarter's ad engagement"

                PARAMETERS:
                - name: audience name (required). Give it something descriptive of the rule, e.g.
                  "Video 50% viewers 90d", so it is recognisable in the audience list later.
                - source_platform: the chosen `engagementSourceType` (required)
                - engagement_trigger: a trigger listed for THAT source type (required). NOTHING
                  VALIDATES THE PAIRING — see the warning below.
                - lookback_window_days: 30, 60, 90, 180 or 365 — WEBSITE caps at 180 (required)
                - engagement_source_urns: LinkedIn URNs from search_linkedin_engagement_sources,
                  copied verbatim. Required for every source type except WEBSITE. Several are
                  normal: the audience is everyone who engaged with ANY of them.
                - page_set_name: internal label for the URL rule set (WEBSITE only, required there).
                  Only ever seen inside LinkedIn, so a plain descriptive label is fine.
                - url_match_groups: the OR-of-ANDs URL expression (WEBSITE only, required there)

                RETURNS:
                Confirmation with the new audience `id` and name, the `criteria` that define it
                (source, trigger, lookback, how many sources), the channel, and a `note` on when it
                becomes usable.

                **WHAT TO TELL THE USER AFTER IT SUCCEEDS:**
                It is created but not yet populated. LinkedIn takes up to 48 hours to build the
                audience and a further 24 hours before it delivers, so it will show NO match count
                and NO contact or company numbers immediately. That is expected and correct, not a
                failure. Say so plainly rather than reporting the audience as empty or broken.

                IMPORTANT NOTES:
                - **THE TRIGGER MUST BELONG TO THE SOURCE TYPE, AND NOTHING CHECKS THAT FOR YOU.**
                  A mismatched pair (e.g. VIDEO_ADS with LEAD_FORM_SUBMIT) is accepted by this tool,
                  by the platform and by LinkedIn, with no error at any layer — it just builds an
                  audience that can never populate, because the engagement it describes cannot
                  happen. Verified on stage. Always take the trigger from the source type's own
                  `triggers` list in step 1; never carry one over from another source type.
                - Requires a connected LinkedIn channel on the account.
                - **NEVER re-create the audience because it shows no members.** Zero right after
                  creation is the normal state; creating it again just makes a duplicate.
                - This audience type NEVER reports contact or company counts the way a firmographic
                  audience does. It lives on LinkedIn, so only LinkedIn's own match count applies.
                - WEBSITE additionally requires the LinkedIn Insight Tag installed and active on the
                  pages the URL rules match. Without it the audience stays empty indefinitely, no
                  matter how long you wait — mention this whenever you build a WEBSITE audience.
                - The lookback window doubles as the retention window: it sets both how far back
                  engagement counts and how long someone stays in the audience.
                - Building from sources with no engagement produces an empty audience. If step 2
                  showed zeros everywhere, raise that with the user instead of creating anyway.
                - The rule cannot be edited afterwards. A different trigger or lookback means a new
                  audience, so confirm the choice before creating when the user was vague.

                COMMON ERRORS AND WHAT THEY MEAN:
                - "engagement_source_urns is required" — you skipped step 2, or passed a WEBSITE-style
                  payload for a non-website source type.
                - "must be one of [30, 60, 90, 180]" — WEBSITE was given a 365-day lookback.
                - "page_set_name / url_match_groups is required" — WEBSITE needs the URL rules, not URNs.